Pediatric Hematology and Oncology

62 questions

All types62 Multiple choice31 Matching16 Ordering15

A 14-month-old boy is brought to the pediatric clinic by his parents due to a persistent, scaly rash on his scalp and behind his ears that has been present for three months. He has also had chronic, bilateral, purulent ear discharge that has not improved despite three separate courses of oral amoxicillin. Recently, his parents noticed he is excessively thirsty and frequently soaks through his diapers, requiring multiple changes at night. On physical examination, the child is irritable but easily consolable. There is an erythematous, crusted, papular rash over the scalp, postauricular regions, and axillae. Abdominal palpation reveals mild hepatosplenomegaly. A skeletal survey is performed and demonstrates a 2.5-cm sharply marginated, "punched-out" lytic lesion in the right parietal bone without surrounding sclerosis. Which of the following is the most likely finding upon histologic or immunohistochemical evaluation of a biopsy from the bone lesion?

Clonal proliferation of cells that express CD1a and S-100 proteins

Heavy infiltration of neutrophils with Gram-positive cocci in clusters

Thickened basement membrane with prominent eosinophilic inclusions

Hyperkeratosis and parakeratosis with abundant Malassezia furfur colonization

Normal trabecular bone architecture with delayed ossification centers

Show answer & explanation

Answer: Clonal proliferation of cells that express CD1a and S-100 proteins

Answer

Clonal proliferation of cells that express CD1a and S-100 proteins

The clinical triad of sharply marginated lytic bone lesions, a seborrheic-like eczematous rash, and central diabetes insipidus (manifesting as polyuria and polydipsia) is classic for Langerhans Cell Histiocytosis (LCH). LCH involves the abnormal clonal proliferation of Langerhans cells, which are specialized dendritic cells of the mononuclear phagocyte system. On immunohistochemical staining, these pathognomonic cells are characteristically positive for CD1a and S-100 surface markers. Furthermore, on electron microscopy, they exhibit distinctive 'tennis racket' shaped intracellular inclusions known as Birbeck granules.

Step-by-Step Solution

Analyze the multi-system clinical presentation.

The 14-month-old presents with a therapy-resistant seborrheic-like rash, chronic ear discharge, and signs of central diabetes insipidus (excessive thirst and polyuria).

Identifying these diverse symptoms as part of a single unifying syndrome is required to avoid premature closure on common, benign pediatric diagnoses.

Interpret the radiographic findings in the context of the physical exam.

The presence of a sharply marginated, 'punched-out' lytic skull lesion without sclerosis, combined with hepatosplenomegaly, points toward a destructive infiltrative process.

Lytic bone lesions in a child rule out simple developmental delays and strongly suggest an oncologic or severe granulomatous disease.

Synthesize the findings to establish the most likely diagnosis.

The classic triad of lytic bone lesions, skin involvement, and central diabetes insipidus is pathognomonic for Hand-Schüller-Christian disease, a systemic variant of Langerhans Cell Histiocytosis (LCH).

Pattern recognition of this triad is essential for identifying this rare pediatric hematology/oncology disorder.

Identify the characteristic histologic and molecular markers for the established diagnosis.

LCH is defined by the clonal proliferation of Langerhans cells, which consistently stain positive for CD1a and S-100 markers.

Definitive diagnosis requires biopsy demonstrating these specific immunohistochemical markers.

Key Concept

Diagnosis and histological hallmarks of Langerhans Cell Histiocytosis (LCH)

Estimated Time:2m 0s

Question 22Question →

Correlate the following pediatric hematology and oncology conditions with their characteristic microscopic, histologic, or laboratory hallmarks.

Click a left item, then click its matching right item

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Answer

Sickle cell disease correlates with Howell-Jolly bodies; hereditary spherocytosis correlates with erythrocytes lacking central pallor; acute lymphoblastic leukemia correlates with TdT-positive lymphoblasts; and neuroblastoma correlates with Homer-Wright rosettes.

Each condition has a pathognomonic diagnostic feature: Sickle cell disease in older children uniformly leads to autosplenectomy, producing Howell-Jolly bodies. Hereditary spherocytosis involves RBC membrane defects resulting in spherocytes and high MCHC. Acute lymphoblastic leukemia originates from immature lymphoid precursors which are universally TdT-positive. Neuroblastoma is an embryonal tumor of the sympathetic nervous system characterized by Homer-Wright rosettes.

Step-by-Step Solution

Evaluate the clinical consequence of sickle cell disease in older children.

Identify that autosplenectomy occurs, leading to the appearance of Howell-Jolly bodies on peripheral smear.

The spleen normally removes these nuclear remnants, but microvascular occlusion destroys splenic function early in childhood.

Recall the classic cellular morphology of hereditary spherocytosis.

Match it with erythrocytes lacking central pallor and an elevated MCHC.

A defect in RBC membrane tethering proteins reduces surface area-to-volume ratio, making the cells round rather than biconcave.

Identify the primary flow cytometry marker for the most common pediatric leukemia (ALL).

Match ALL with TdT-positive lymphoblasts.

TdT is a classic marker of early lymphoid differentiation, distinguishing lymphoblasts from myeloblasts.

Recall the classic histologic finding for neuroblastoma.

Match it with Homer-Wright rosettes.

These rosettes are characteristic of several pediatric neural crest and embryonal tumors, most notably neuroblastoma.

Key Concept

Classic pathologic and laboratory findings in pediatric hematology and oncology

Estimated Time:45s

Question 23Question →

Emergency medical services arrive with a 7-year-old male who has homozygous sickle cell disease (HbSS). His parents report that he abruptly developed right arm paralysis and lost the ability to speak approximately 45 minutes ago. His temperature is $37.0^\circ\text{C}$ ( $98.6^\circ\text{F}$ ), blood pressure is $112/72 \text{ mm Hg}$ , pulse is $118\text{/min}$ , and respirations are $22\text{/min}$ . Oxygen saturation is $98\%$ on room air. Neurological examination reveals a right-sided facial droop, expressive aphasia, and $2/5$ muscle strength in the right upper and lower extremities. Laboratory studies show a hemoglobin of $7.5 \text{ g/dL}$ , hematocrit of $22\%$ , and a reticulocyte count of $12\%$ . Arrange the following steps in the most appropriate chronological sequence for the comprehensive immediate and long-term management of this patient.

Drag items to arrange them in the correct order

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Answer

The most appropriate chronological sequence is: 1) Non-contrast CT scan of the head, 2) Partial exchange blood transfusion, 3) MRI/MRA of the brain and neck, 4) Scheduled chronic red blood cell transfusions, 5) Evaluation for hematopoietic stem cell transplantation.

The correct sequence fundamentally follows the principles of pediatric trauma and emergency neurology: stabilize and rule out immediately life-threatening complications (hemorrhage via CT), provide acute disease-specific intervention (exchange transfusion for sickle cell stroke), completely define the pathology once stable (MRI/MRA), prevent recurrence (chronic transfusions), and finally seek a definitive cure (stem cell transplant evaluation).

Step-by-Step Solution

Assess airway, breathing, circulation, and rule out intracranial hemorrhage.

Perform an emergent non-contrast CT of the head.

Although ischemic stroke is more common in children with sickle cell disease, hemorrhagic stroke must be excluded rapidly because it completely alters the acute management pathway and makes certain transfusion strategies hazardous.

Treat the acute vaso-occlusive crisis in the cerebral vasculature.

Perform a partial exchange red blood cell transfusion.

An exchange transfusion rapidly decreases the proportion of sickled cells (target HbS < 30%) and improves cerebral oxygen delivery. Simple transfusion is typically avoided if it risks raising the total hemoglobin too high, which could cause hyperviscosity and worsen the stroke.

Define the precise vascular anatomy and the extent of the infarction.

Obtain an MRI and MRA of the brain and neck.

Once the patient is out of immediate danger, advanced imaging is essential for mapping the ischemic penumbra and identifying concurrent structural vasculopathy, which guides long-term neurosurgical or hematological planning.

Implement secondary stroke prevention.

Initiate a chronic monthly red blood cell transfusion program.

Without secondary prophylaxis, the recurrence rate of stroke in sickle cell disease is extremely high. Chronic transfusions significantly reduce this risk.

Provide a definitive, curative treatment plan.

Evaluate for an HLA-matched sibling hematopoietic stem cell transplantation.

HSCT is the only curative therapy for sickle cell disease. It is strongly indicated for patients who have already suffered severe, irreversible complications such as an overt stroke.

Key Concept

The management sequence for acute ischemic stroke in pediatric sickle cell disease progresses from emergent diagnostics to rule out bleeding, to acute exchange transfusion, to detailed neuroimaging, followed by secondary prevention, and ultimately curative evaluation.

Question 24Question →

A 6-year-old girl is brought to the emergency department by her parents due to a sudden onset of fever. She was diagnosed with acute lymphoblastic leukemia (ALL) six months ago and is currently undergoing maintenance chemotherapy. Her temperature is $39.4^\circ C$ ( $102.9^\circ F$ ), blood pressure is $90/55$ mmHg, and heart rate is $125$ /min. Physical examination reveals a pale, fatigued child with a central venous catheter in place. There is no erythema or discharge at the catheter site. Laboratory studies show an absolute neutrophil count (ANC) of $350/mm^3$ . Blood cultures are obtained. Which of the following is the most appropriate next step in management?

Administer the live-attenuated varicella vaccine to prevent viral co-infection.

Prescribe oral amoxicillin to align with antibiotic stewardship guidelines.

Initiate empiric broad-spectrum intravenous antibiotics immediately.

Await blood culture results before initiating any antimicrobial therapy.

Administer nebulized bronchodilators for a presumed viral respiratory infection.

Show answer & explanation

Answer: Initiate empiric broad-spectrum intravenous antibiotics immediately.

Answer

Initiate empiric broad-spectrum intravenous antibiotics immediately.

This patient has febrile neutropenia, clinically defined as a single oral temperature of

\geq 38.3^\circ C

(

101^\circ F

) or sustained temperature

\geq 38.0^\circ C

(

100.4^\circ F

) for

\geq 1

hour in the setting of an absolute neutrophil count (ANC) below

500/mm^3

. Because immunocompromised patients lack the white blood cells necessary to mount a standard inflammatory response, a bacterial infection can rapidly progress to life-threatening sepsis. Therefore, the immediate administration of empiric broad-spectrum intravenous antibiotics with antipseudomonal activity (such as cefepime, meropenem, or piperacillin-tazobactam) is the most critical next step immediately after obtaining blood cultures.

Step-by-Step Solution

Identify the primary clinical problem from the vignette.

The patient is a pediatric oncology patient on chemotherapy presenting with a fever (

39.4^\circ C

) and an absolute neutrophil count of

350/mm^3

Recognizing the combination of fever and severe neutropenia (ANC <

500/mm^3

) establishes the diagnosis of febrile neutropenia.

Determine the standard emergency management protocol for this condition.

Immediate administration of empiric broad-spectrum intravenous antibiotics.

Patients with severe neutropenia cannot mount an adequate cellular immune response. Delaying antimicrobial therapy can rapidly lead to overwhelming, fatal sepsis.

Key Concept

Febrile neutropenia is a medical emergency requiring immediate empiric broad-spectrum intravenous antibiotics (e.g., cefepime, piperacillin-tazobactam) after obtaining blood cultures.

Estimated Time:1m 0s

Question 25Question →

A $7$ -year-old boy is admitted to the pediatric intensive care unit for the initiation of chemotherapy for newly diagnosed, advanced-stage Burkitt lymphoma. He has a massive abdominal tumor burden. A central venous port was placed $48$ hours ago. Twelve hours after receiving his first dose of chemotherapy, he becomes lethargic and his urine output drops to $0.2 \text{ mL/kg/hr}$ .

Continuous telemetry reveals peaked T waves and a widened QRS complex.

Temperature is $38.6^\circ \text{C}$ ( $101.5^\circ \text{F}$ ), blood pressure is $90/55 \text{ mm Hg}$ , pulse is $135/\text{min}$ , and respiratory rate is $28/\text{min}$ . Initial blood cultures drawn from the port at the time of admission are now growing *Escherichia coli* that is susceptible to ceftriaxone.

Laboratory studies reveal the following:

Laboratory Parameter	Value
Sodium ( $Na^+$ )	$134 \text{ mEq/L}$
Potassium ( $K^+$ )	$7.2 \text{ mEq/L}$
Chloride ( $Cl^-$ )	$98 \text{ mEq/L}$
Bicarbonate ( $HCO_3^-$ )	$12 \text{ mEq/L}$
Calcium ( $Ca^{2+}$ )	$6.1 \text{ mg/dL}$
Phosphorus	$9.5 \text{ mg/dL}$
Uric acid	$16.2 \text{ mg/dL}$
Blood urea nitrogen (BUN)	$58 \text{ mg/dL}$
Creatinine	$2.4 \text{ mg/dL}$ (baseline $0.6 \text{ mg/dL}$ )

An arterial blood gas on room air shows a pH of $7.26$ , $pCO_2$ of $26 \text{ mm Hg}$ , and $pO_2$ of $92 \text{ mm Hg}$ . Upon reviewing his chart, the parents note he missed his $4$ -year-old immunization boosters and ask if they can be updated while he is hospitalized.

Which of the following is the most appropriate initial step in the management of this patient?

Administer intravenous sodium bicarbonate infusion to correct the uncompensated respiratory acidosis that is shifting potassium extracellularly

Initiate broad-spectrum intravenous vancomycin and meropenem to provide empiric coverage for his bacteremia despite current culture sensitivities

Administer intravenous calcium gluconate followed by regular insulin with dextrose, and prepare for emergent hemodialysis

Order a venous Doppler ultrasound of the upper extremity, as fever occurring exactly 48 hours postoperatively is most characteristic of deep vein thrombosis

Administer the live-attenuated measles, mumps, and rubella (MMR) and varicella vaccines to protect his immunocompromised system prior to discharge

Show answer & explanation

Answer: Administer intravenous calcium gluconate followed by regular insulin with dextrose, and prepare for emergent hemodialysis

Answer

The most appropriate initial step is to administer intravenous calcium gluconate followed by regular insulin with dextrose, and prepare for emergent hemodialysis.

This patient is presenting with severe Tumor Lysis Syndrome (TLS), a rapidly developing oncologic emergency characterized by the massive release of intracellular contents following the destruction of malignant cells (especially in highly proliferative tumors like Burkitt lymphoma). He has the hallmark laboratory triad of hyperuricemia, hyperkalemia, and hyperphosphatemia with secondary hypocalcemia. The most immediate threat to his life is the potassium of

7.2 \text{ mEq/L}

with accompanying EKG changes (peaked T waves, widened QRS), indicating imminent cardiac arrest. The immediate next step must be intravenous calcium gluconate to stabilize the myocardial membrane, followed by regular insulin (with dextrose) to shift potassium intracellularly. Because he is oliguric with acute kidney injury, these bridging measures must be immediately followed by emergent hemodialysis for definitive clearance.

Step-by-Step Solution

Analyze the patient's clinical presentation and comprehensive laboratory profile.

The patient has hyperuricemia, hyperphosphatemia, hypocalcemia, hyperkalemia, and oliguric acute kidney injury following the initiation of chemotherapy for Burkitt lymphoma.

These findings represent the classic triad of metabolic derangements diagnostic of severe Tumor Lysis Syndrome (TLS), complicated by acute renal failure.

Evaluate the telemetry findings and specific electrolyte critical values.

The potassium level is critically elevated at

7.2 \text{ mEq/L}

, accompanied by peaked T waves and a widened QRS complex on the electrocardiogram.

Severe hyperkalemia with EKG changes is an immediate, life-threatening medical emergency that can rapidly degenerate into ventricular fibrillation or asystole.

Determine the prioritized management sequence based on the most immediate threat to life.

The immediate priority is to stabilize the cardiac membrane with intravenous calcium gluconate, shift potassium intracellularly using insulin with dextrose, and prepare for emergent hemodialysis to definitively clear the potassium and uric acid.

While the patient has concurrent issues (bacteremia, acidosis), preventing imminent cardiac arrest from hyperkalemia supersedes all other diagnostic and therapeutic interventions.

Key Concept

Management of life-threatening hyperkalemia in Tumor Lysis Syndrome

Estimated Time:3m 0s

Question 26Question →

Match the following pediatric hematologic malignancies with their characteristic molecular, cytogenetic, or immunophenotypic findings.

Click a left item, then click its matching right item

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Answer

B-ALL matches CD10/CD19 positivity with t(12;21); T-ALL matches the mediastinal mass and CD2/CD3/CD7 expression; Burkitt Lymphoma matches the t(8;14) translocation and 'starry sky' histology; ALCL matches the t(2;5) NPM-ALK fusion and CD30 positivity; and JMML matches RAS pathway mutations with GM-CSF hypersensitivity.

Each pediatric malignancy has a unique defining signature. B-ALL is recognized by its CD10/CD19 positivity and t(12;21) or hyperdiploidy. T-ALL is uniquely associated with mediastinal masses and CD2/CD3/CD7 expression. Burkitt Lymphoma relies on the t(8;14) c-MYC translocation causing rapid proliferation ('starry sky'). ALCL is defined by t(2;5) NPM-ALK fusions and CD30+ hallmark cells. Finally, JMML is a distinct myeloproliferative disorder identified by RAS pathway mutations and diagnostic GM-CSF hypersensitivity.

Step-by-Step Solution

Identify the diagnostic hallmarks of Pediatric B-cell Acute Lymphoblastic Leukemia (B-ALL).

Matched with TdT, CD10, and CD19 positivity, alongside favorable cytogenetics like hyperdiploidy or t(12;21).

Recognizing the distinct surface markers and favorable cytogenetics separates B-ALL from other leukemias.

Identify the clinical and immunophenotypic presentation of Pediatric T-cell Acute Lymphoblastic Leukemia (T-ALL).

Matched with an anterior mediastinal mass and T-cell markers such as CD2, CD3, and CD7.

The anterior mediastinal mass (often compressing the SVC or airway) and T-cell surface antigens are primary distinguishing features for T-ALL.

Determine the genetic and histologic features of Burkitt Lymphoma.

Matched with the t(8;14) translocation causing c-MYC overexpression and a 'starry sky' pattern on histology.

The c-MYC translocation is the fundamental oncogenic driver of Burkitt Lymphoma, leading to extreme proliferation and high macrophage clearing activity.

Match Anaplastic Large Cell Lymphoma (ALCL) to its specific molecular abnormality.

Matched with the t(2;5) translocation producing the NPM-ALK fusion protein and CD30 expression.

The ALK fusion protein is the defining molecular feature of pediatric ALCL, presenting with large anaplastic cells.

Identify the underlying pathogenesis of Juvenile Myelomonocytic Leukemia (JMML).

Matched with hyperactivation of the RAS pathway and profound in vitro hypersensitivity of myeloid progenitors to GM-CSF.

JMML requires specific pathway mutations for diagnosis, making it clinically distinct from classic acute leukemias.

Key Concept

Molecular and immunophenotypic characterization of pediatric hematologic malignancies.

Question 27Question →

A 6-year-old boy is brought to the emergency department by his parents due to progressive lethargy, weakness, and severe pallor over the past 2 days. One week ago, he had a low-grade fever, rhinorrhea, and a brightly erythematous rash on both cheeks that spared his nasal bridge. His past medical history is significant for neonatal jaundice requiring 4 days of phototherapy. His father underwent a cholecystectomy at age 22. Vital signs show a temperature of 37.1°C (98.8°F), heart rate of 135/min, and blood pressure of 90/60 mm Hg. Physical examination reveals marked conjunctival pallor and a palpable spleen 4 cm below the left costal margin. Laboratory studies reveal the following:

Laboratory test	Result
Hemoglobin	4.5 g/dL
Mean corpuscular volume (MCV)	81 fL
Mean corpuscular hemoglobin concentration (MCHC)	37.5 g/dL
Platelets	250,000/mm³
Leukocytes	7,200/mm³
Reticulocytes	0.1%

Which of the following is the most likely primary mechanism for this patient's current severe anemia?

Viral-induced arrest of erythroid progenitor cells

Accelerated macrophage-mediated destruction of erythrocytes

Depletion of required micronutrients for DNA synthesis

Rapid pooling of circulating erythrocytes within the splenic parenchyma

Autoantibody-mediated complement activation and intravascular hemolysis

Show answer & explanation

Answer: Viral-induced arrest of erythroid progenitor cells

Answer

Viral-induced arrest of erythroid progenitor cells

The correct answer describes the pathogenesis of an aplastic crisis caused by Parvovirus B19. The patient's underlying hereditary spherocytosis is indicated by the family history of early gallstones, neonatal jaundice requiring phototherapy, splenomegaly, and an elevated mean corpuscular hemoglobin concentration (MCHC). The recent 'slapped cheek' rash strongly points to a recent Parvovirus B19 infection. This virus has a strong tropism for erythroid precursors in the bone marrow, where it replicates and causes cell death, leading to a temporary halt in erythropoiesis. In a healthy individual, this transient arrest is usually asymptomatic. However, in a patient with a chronic hemolytic anemia like hereditary spherocytosis—who relies on continuous, high-volume red blood cell production to maintain baseline hemoglobin levels—this sudden halt results in a rapid, severe anemia characterized by an inappropriately low reticulocyte count.

Step-by-Step Solution

Identify the underlying chronic condition from the patient's history and baseline laboratory clues.

The history of neonatal jaundice, early-onset gallstones in the father (pigment stones), splenomegaly, and an elevated MCHC (>36 g/dL) strongly point to Hereditary Spherocytosis.

Recognizing the chronic hemolytic baseline is essential to understanding why the patient decompensated so rapidly.

Identify the acute precipitating event from the recent clinical history.

The recent febrile illness with a brightly erythematous rash on the cheeks ('slapped cheek' appearance) is the classic presentation of Erythema infectiosum, caused by Parvovirus B19.

The trigger explains the acute change in the patient's clinical status.

Correlate the infectious trigger with the current laboratory findings to determine the mechanism of anemia.

Parvovirus B19 infects erythroid precursors in the bone marrow, temporarily halting red blood cell production. In a patient with chronic hemolysis (like Hereditary Spherocytosis), this leads to a rapid, severe drop in hemoglobin accompanied by an inappropriately low reticulocyte count (0.1%).

This confirms the diagnosis of an aplastic crisis rather than a hemolytic or sequestration crisis.

Key Concept

Aplastic crisis in Hereditary Spherocytosis secondary to Parvovirus B19 infection.

Estimated Time:1m 30s

Question 28Question →

A 5-year-old boy is brought to the emergency department by his parents due to extreme fatigue, decreased urination over the past 24 hours, and a new rash. One week ago, he had a 3-day episode of severe, bloody diarrhea accompanied by abdominal cramps, which was treated with oral ciprofloxacin at an urgent care clinic. Today, he appears pale and lethargic. Vitals show a temperature of $37.2^\circ\text{C}$ , heart rate of $135/\text{min}$ , respiratory rate of $24/\text{min}$ , and blood pressure of $118/78 \text{ mmHg}$ . Physical examination reveals scleral icterus and scattered petechiae over the lower extremities. The abdomen is soft and non-tender with no hepatosplenomegaly. Laboratory studies show:

Laboratory Study	Result
Hemoglobin	$6.8 \text{ g/dL}$
Platelets	$38,000/\text{mm}^3$
Leukocytes	$14,500/\text{mm}^3$
Blood Urea Nitrogen (BUN)	$52 \text{ mg/dL}$
Creatinine	$2.4 \text{ mg/dL}$

A peripheral blood smear demonstrates numerous fragmented red blood cells. Which of the following is the most appropriate next step in the management of this patient?

Supportive care with intravenous fluid resuscitation and close monitoring

Intravenous ceftriaxone therapy

Platelet transfusion

Plasma exchange (plasmapheresis)

High-dose intravenous corticosteroids

Show answer & explanation

Answer: Supportive care with intravenous fluid resuscitation and close monitoring

Answer

The most appropriate next step in management is supportive care with intravenous fluid resuscitation and close monitoring.

Supportive care with intravenous fluid resuscitation and close monitoring is the correct management. The patient's presentation of microangiopathic hemolytic anemia (schistocytes, low hemoglobin, jaundice), thrombocytopenia (petechiae), and acute kidney injury (oliguria, elevated BUN/creatinine) following a bloody diarrheal illness is the classic triad of Hemolytic Uremic Syndrome (HUS). This condition is most commonly caused by Shiga toxin-producing E. coli (STEC), especially O157:H7. The cornerstone of management for typical STEC-HUS is entirely supportive, focusing on rigorous fluid balance to maintain renal perfusion, electrolyte correction, and red blood cell transfusions if anemia is severe or symptomatic. The prior inappropriate use of a fluoroquinolone likely increased toxin release and precipitated the condition.

Step-by-Step Solution

Identify the classic triad in the clinical vignette.

The patient has microangiopathic hemolytic anemia (schistocytes, jaundice, low hemoglobin), thrombocytopenia (petechiae), and acute kidney injury (oliguria, elevated BUN/creatinine).

Recognizing this triad is essential for diagnosing the underlying syndrome.

Correlate the triad with the recent history.

The recent bloody diarrhea establishes the diagnosis of typical Hemolytic Uremic Syndrome (HUS), most commonly caused by Shiga toxin-producing E. coli (STEC).

Differentiating typical (diarrhea-associated) HUS from atypical HUS or TTP dictates specific management.

Evaluate the impact of the prior antibiotic administration.

The prior ciprofloxacin treatment likely exacerbated the condition, as antibiotics increase Shiga toxin release from dying bacteria.

Understanding the harm of antibiotics in this context reinforces why further pharmacologic intervention may be detrimental.

Determine the standard of care for typical pediatric STEC-HUS.

Management is purely supportive, prioritizing intravenous fluid expansion (which protects renal perfusion), electrolyte management, and packed red blood cell transfusions if anemia is severe or symptomatic.

Invasive or specific targeted therapies like plasmapheresis or platelet transfusions are either ineffective or actively harmful in typical STEC-HUS.

Key Concept

Typical (STEC-associated) Hemolytic Uremic Syndrome (HUS) is managed with supportive care, particularly volume expansion and monitoring. Antibiotics and platelet transfusions are generally contraindicated as they can exacerbate the microangiopathic process.

Question 29Question →

Emergency medical personnel transport an 18-month-old boy to the emergency department due to progressive lethargy and severe pallor over the past 12 hours. The patient has a known history of sickle cell disease (HbSS) and is currently prescribed daily penicillin prophylaxis. Upon arrival, his temperature is $37.0^\circ\text{C}$ ( $98.6^\circ\text{F}$ ), heart rate is $172/\text{min}$ , respiratory rate is $44/\text{min}$ , and blood pressure is $65/35\text{ mm Hg}$ . Physical examination reveals a somnolent toddler with marked conjunctival pallor, delayed capillary refill of 4 seconds, and cool, clammy extremities. Abdominal examination demonstrates significant distension and a firm, tender mass extending $6\text{ cm}$ below the left costal margin. Laboratory studies reveal the following:

* Hemoglobin: $3.8\text{ g/dL}$ (baseline $8.2\text{ g/dL}$ )
* Reticulocytes: $16\%$
* Platelets: $45,000/\text{mm}^3$
* Leukocytes: $14,000/\text{mm}^3$

Which of the following is the most appropriate next step in the management of this patient?

Intravenous administration of isotonic crystalloids and packed red blood cells

Computed tomography of the abdomen with intravenous contrast

Emergent exploratory laparotomy and splenectomy

Bone marrow aspiration and biopsy

Observation with serial abdominal girth measurements

Show answer & explanation

Answer: Intravenous administration of isotonic crystalloids and packed red blood cells

Answer

Intravenous administration of isotonic crystalloids and packed red blood cells

This patient is presenting with acute splenic sequestration crisis, a life-threatening complication seen primarily in young children with sickle cell disease (typically between 6 months and 3 years of age, before the spleen auto-infarcts). The condition occurs when vaso-occlusion within the splenic vasculature causes massive pooling of red blood cells in the spleen. This results in acute splenomegaly, a precipitous drop in hemoglobin levels, and potentially fatal hypovolemic shock. The trapping of platelets also frequently causes mild to moderate thrombocytopenia. Crucially, the bone marrow responds appropriately to the severe anemia, leading to a marked elevation in reticulocytes. The immediate priority in management is the reversal of hypovolemic shock and severe anemia. Therefore, the rapid intravenous administration of isotonic crystalloids (to expand intravascular volume) and packed red blood cells (to restore oxygen-carrying capacity and correct the profound anemia) is the most appropriate next step.

Step-by-Step Solution

Analyze the patient's vital signs and physical examination.

The patient has marked tachycardia (

172/\text{min}

), hypotension (

65/35\text{ mm Hg}

), delayed capillary refill, and altered mental status (somnolence), indicating severe uncompensated hypovolemic shock.

Recognizing the presence of shock dictates the urgency and direction of initial management.

Interpret the laboratory findings in the context of the physical examination.

The precipitous drop in hemoglobin (

3.8\text{ g/dL}

), concurrent thrombocytopenia (

45,000/\text{mm}^3

), and robust reticulocyte count (

16\%

) alongside massive splenomegaly confirm a diagnosis of acute splenic sequestration crisis.

Differentiating sequestration (high reticulocytes, large spleen) from aplastic crisis (low reticulocytes, no splenomegaly) is critical for targeted therapy.

Determine the most appropriate immediate intervention based on the primary pathophysiology.

The primary cause of imminent death is intravascular volume depletion due to red blood cell trapping in the spleen; therefore, rapid volume expansion and correction of severe anemia are required.

Immediate survival depends on reversing hypovolemia and restoring tissue oxygenation before pursuing definitive long-term treatments like splenectomy.

Key Concept

Acute splenic sequestration crisis is a life-threatening emergency in young children with sickle cell disease characterized by rapid splenic pooling of red blood cells, leading to severe anemia, hypovolemic shock, and compensatory reticulocytosis. Initial management requires immediate volume resuscitation and blood transfusion.

Question 30Question →

Parents bring their 24-month-old daughter to the emergency department because she has been refusing to stand or walk for the past 48 hours. They also report that she developed new-onset urinary incontinence this morning. The patient appears irritable but is consolable. Temperature is $37.2^\circ\text{C}$ ( $99.0^\circ\text{F}$ ), blood pressure is $115/70\text{ mmHg}$ , and heart rate is $120\text{/min}$ . Physical examination reveals a firm, irregular, palpable abdominal mass crossing the midline. Neurologic examination of the lower extremities shows $2/5$ motor strength bilaterally, $3+$ patellar and Achilles deep tendon reflexes, and a positive Babinski sign bilaterally. Anal sphincter tone is decreased.

Based on the most likely diagnosis, arrange the following management steps in the most appropriate chronological order of execution.

Drag items to arrange them in the correct order

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Answer

The correct chronological order is: 1) Administer high-dose intravenous dexamethasone, 2) Perform urgent magnetic resonance imaging (MRI) of the spine, 3) Consult neurosurgery or radiation oncology for definitive local decompression, 4) Perform an image-guided biopsy of the abdominal mass.

In the setting of suspected malignant spinal cord compression (suggested by the new-onset upper motor neuron signs, paraparesis, and bowel/bladder dysfunction in a patient with a probable neuroblastoma), the immediate priority is protecting the spinal cord. High-dose corticosteroids (dexamethasone) reduce peritumoral edema and must be given as the absolute first step. Once steroids are on board, MRI is performed to confirm and map the compression. This is followed by definitive local therapy (surgery or radiation). Finally, after the neurological emergency is stabilized, a biopsy of the primary mass is performed to guide long-term systemic chemotherapy.

Step-by-Step Solution

Identify the clinical syndrome and underlying etiology.

The patient exhibits upper motor neuron signs (hyperreflexia, positive Babinski), weakness, and autonomic dysfunction (incontinence) combined with an abdominal mass crossing the midline.

These findings are highly indicative of neuroblastoma with paraspinal extension causing malignant spinal cord compression, which is an oncologic emergency.

Determine the most critical, immediate intervention.

Intravenous dexamethasone is administered first.

Corticosteroids rapidly reduce vasogenic edema surrounding the compressed spinal cord, preserving neurologic function. This must precede any diagnostic imaging to prevent permanent paraplegia.

Establish the sequence for diagnostic imaging and structural intervention.

MRI of the spine is ordered next, followed by neurosurgical or radiation oncology consultation.

Imaging is required to localize the exact site of compression. Once localized, mechanical decompression (via surgery or radiation) is needed to treat the structural emergency.

Determine the timing for establishing a definitive tissue diagnosis.

Biopsy of the abdominal mass is placed last.

While essential for dictating systemic chemotherapy, obtaining a tissue diagnosis is not immediately limb- or life-saving and must wait until the acute neurological threat is neutralized.

Key Concept

Management sequence for malignant spinal cord compression in pediatric oncology.

Estimated Time:1m 30s

Question 31Question →

Congenital bone marrow failure syndromes and inherited cytopenias in pediatric oncology often present with characteristic combinations of hematologic laboratory abnormalities and physical exam findings. Match each of the following patient clinical vignettes with the most likely underlying syndromic diagnosis.

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Answer

The correct matches align each clinical vignette with its classic syndromic diagnosis: The 4-month-old with isolated macrocytic anemia and triphalangeal thumbs has Diamond-Blackfan anemia; the 8-year-old with pancytopenia and absent thumbs has Fanconi anemia; the 2-year-old with neutropenia, steatorrhea, and metaphyseal dysostosis has Shwachman-Diamond syndrome; the 12-year-old with bone marrow failure and a mucocutaneous triad has Dyskeratosis congenita; and the newborn with thrombocytopenia and absent radii but preserved thumbs has Thrombocytopenia-absent radius (TAR) syndrome.

Each patient presentation contains classic, distinguishing features for a specific bone marrow failure syndrome. Diamond-Blackfan anemia is characterized by pure red cell aplasia and triphalangeal thumbs. Fanconi anemia features pancytopenia, absent thumbs, and café-au-lait macules. Shwachman-Diamond syndrome presents with neutropenia and exocrine pancreatic insufficiency. Dyskeratosis congenita is defined by marrow failure and a mucocutaneous triad. TAR syndrome is distinct for severe thrombocytopenia and absent radii with preserved thumbs.

Step-by-Step Solution

Analyze the specific hematologic abnormality in each patient vignette.

The 4-month-old has pure red cell aplasia; the 8-year-old has progressive pancytopenia; the 2-year-old has severe neutropenia; the 12-year-old has progressive bone marrow failure; the newborn has isolated severe thrombocytopenia.

Identifying the specific affected cell line(s) narrows the differential diagnosis for inherited bone marrow failure syndromes.

Evaluate the associated physical exam anomalies and age of onset.

The 4-month-old has triphalangeal thumbs; the 8-year-old has absent thumbs and café-au-lait spots; the 2-year-old has malabsorption and skeletal dysplasia; the 12-year-old has a mucocutaneous triad; the newborn has absent radii with present thumbs.

These physical findings are pathognomonic and allow for precise differentiation among the genetic syndromes.

Key Concept

Differentiation of pediatric congenital bone marrow failure syndromes relies on identifying the specific affected cell line (e.g., RBCs vs. platelets vs. all lines) combined with highly characteristic physical anomalies (e.g., thumb presentation, mucocutaneous findings).

Question 32Question →

A pediatric patient with a known history of severe hemophilia A is evaluated for acute-onset right knee pain and swelling. The child's caregivers administered the prescribed on-demand recombinant factor VIII concentrate twice over the preceding 24 hours; however, the joint effusion and pain have continued to worsen. He currently refuses to bear weight on the affected limb. Vital signs show a temperature of 37.1°C (98.8°F), heart rate of 110/min, and blood pressure of 100/65 mm Hg. Physical examination reveals a tense, warm, and highly tender right knee with a restricted range of motion. Laboratory evaluation demonstrates a normal prothrombin time (PT) and a significantly prolonged activated partial thromboplastin time (aPTT). An incubation mixing study is performed; the aPTT fails to correct upon the addition of normal plasma. Which of the following is the most appropriate next step in management?

Intravenous recombinant factor VIIa

Continuous infusion of high-dose factor VIII

Intravenous desmopressin

Diagnostic arthrocentesis of the right knee

Transfusion of fresh frozen plasma

Show answer & explanation

Answer: Intravenous recombinant factor VIIa

Answer

Intravenous recombinant factor VIIa

The correct intervention involves utilizing a bypassing agent. This patient has severe hemophilia A and presents with an acute hemarthrosis that is refractory to his usual factor VIII therapy. The critical diagnostic clue is the mixing study: the failure of the prolonged aPTT to correct when mixed with normal plasma confirms the presence of a circulating inhibitor (alloantibodies against factor VIII). In patients with functionally significant inhibitors, administering more factor VIII is ineffective because the antibodies neutralize the replacement factor. Instead, hemostasis must be achieved using bypassing agents, such as recombinant factor VIIa or activated prothrombin complex concentrate (aPCC). These agents bypass the factor VIII-dependent step in the intrinsic coagulation cascade to directly promote factor X activation and subsequent thrombin generation.

Step-by-Step Solution

Interpret the clinical presentation and response to prior therapy.

The patient has an acute hemarthrosis that is refractory to his standard recombinant factor VIII therapy.

Lack of clinical improvement after two appropriate on-demand doses suggests decreased efficacy of the administered factor.

Analyze the coagulation laboratory results, specifically the mixing study.

The aPTT does not correct after incubating with normal plasma.

Normal plasma contains factor VIII. If the patient had a simple factor deficiency, the normal plasma would correct the aPTT. Failure to correct indicates the presence of a circulating alloantibody (inhibitor) neutralizing factor VIII.

Determine the appropriate management for an acute bleed in the setting of a factor VIII inhibitor.

Bypass agents are required to achieve hemostasis.

Because factor VIII is neutralized by antibodies, hemostasis must be achieved by bypassing the intrinsic pathway. Recombinant factor VIIa (or activated prothrombin complex concentrate) directly activates factor X, promoting clot formation.

Key Concept

Management of hemophilia A complicated by the development of factor VIII inhibitors (alloantibodies) using bypassing agents.

Question 33Question →

An $8$ -year-old boy is evaluated on the pediatric ward for sudden onset of respiratory distress. He has a medical history significant for homozygous hemoglobin S disease. He was admitted $2$ days ago for a severe vaso-occlusive pain episode affecting his bilateral lower extremities, which has been managed with intravenous hydration and morphine. Today, he developed a new-onset fever with a temperature of $39.2^\circ\text{C}$ , a respiratory rate of $32/\text{min}$ , and sharp right-sided chest pain. Pulse oximetry shows an oxygen saturation of $87\%$ on room air. Physical examination reveals decreased breath sounds and crackles in the right lower lung field. Laboratory studies show that his hemoglobin level has dropped from a baseline of $8.2\text{ g/dL}$ to $6.1\text{ g/dL}$ , and his leukocyte count is $18,500/\text{\mu L}$ . A chest radiograph demonstrates a new right lower lobe consolidation. Which of the following is the most appropriate next step in the management of this patient?

Red blood cell transfusion and intravenous administration of a third-generation cephalosporin and a macrolide

Administration of systemic corticosteroids, inhaled albuterol, and a viral respiratory panel

Intravenous administration of furosemide and strict fluid restriction

Empiric administration of intravenous vancomycin and piperacillin-tazobactam while withholding blood transfusion

Immediate transport to radiology for a computed tomography pulmonary angiography

Show answer & explanation

Answer: Red blood cell transfusion and intravenous administration of a third-generation cephalosporin and a macrolide

Answer

Red blood cell transfusion combined with intravenous administration of a third-generation cephalosporin and a macrolide.

The patient's presentation of fever, chest pain, tachypnea, hypoxia, and a new pulmonary infiltrate in the setting of homozygous sickle cell anemia is diagnostic of acute chest syndrome (ACS). ACS is a medical emergency characterized by a vicious cycle of hypoxia leading to further red blood cell sickling and pulmonary infarction. The most appropriate initial management includes supplemental oxygen, pain control, empiric antibiotics covering both typical and atypical respiratory pathogens (such as a third-generation cephalosporin and a macrolide), and a red blood cell transfusion. Transfusion (simple or exchange, depending on severity) is the definitive therapy to increase the oxygen-carrying capacity and decrease the percentage of hemoglobin S, thereby breaking the sickling cycle.

Step-by-Step Solution

Identify the primary complication based on the clinical presentation.

The patient has fever, hypoxia, chest pain, and a new pulmonary infiltrate on chest X-ray in the context of sickle cell anemia, which confirms the diagnosis of Acute Chest Syndrome (ACS).

Establishing the correct diagnosis is essential to distinguish ACS from isolated pneumonia, asthma, or fluid overload.

Determine the underlying pathophysiology requiring urgent intervention.

Hypoxia, infection, and inflammation are inducing further hemoglobin S polymerization, leading to worsening pulmonary infarction and a rapidly dropping hemoglobin level.

Understanding the sickling cycle highlights the critical need to not just treat the infection, but to directly improve oxygen-carrying capacity and dilute the sickle hemoglobin.

Select the comprehensive treatment bundle.

The patient urgently requires a red blood cell transfusion to reduce the HbS fraction, alongside atypical and typical bacterial coverage (cephalosporin and macrolide).

RBC transfusion definitively breaks the cycle of sickling, while targeted antibiotics treat the most common infectious triggers of ACS.

Key Concept

Diagnosis and management of Acute Chest Syndrome in pediatric patients with sickle cell disease.

Estimated Time:1m 30s

Question 34Question →

Match each pediatric patient's clinical presentation and associated diagnostic findings with the most likely central nervous system tumor.

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Answer

Pilocytic astrocytoma pairs with the cystic cerebellar mass containing Rosenthal fibers. Medulloblastoma pairs with the solid vermis mass containing Homer-Wright rosettes. Ependymoma pairs with the fourth ventricle mass containing perivascular pseudorosettes. Craniopharyngioma pairs with the suprasellar calcified mass.

Each pediatric brain tumor has a highly specific combination of anatomical location, imaging characteristics, and histology. Pilocytic astrocytoma is typically cystic with a mural nodule in the cerebellum and features Rosenthal fibers. Medulloblastoma is a solid vermis tumor characterized by Homer-Wright rosettes. Ependymoma occurs directly in the fourth ventricle with perivascular pseudorosettes. Craniopharyngioma is a suprasellar mass frequently causing bitemporal hemianopsia and pituitary dysfunction.

Step-by-Step Solution

Analyze the neuroimaging features and location for each presentation.

Identified a cystic cerebellar mass, a solid cerebellar mass, a distinct fourth ventricle mass, and a suprasellar mass.

Tumor location (e.g., suprasellar vs. infratentorial) and appearance (cystic vs. solid) narrow down the differential diagnosis for pediatric brain tumors.

Correlate imaging findings with specific histopathologic hallmarks.

Matched eosinophilic inclusions (Rosenthal fibers) to pilocytic astrocytoma, Homer-Wright rosettes to medulloblastoma, perivascular pseudorosettes to ependymoma, and calcified Rathke pouch remnants to craniopharyngioma.

Histology provides the definitive diagnosis and uniquely distinguishes between tumors that occur in similar anatomical locations.

Key Concept

Integration of neuroimaging characteristics, anatomical location, and specific histopathological findings in diagnosing pediatric CNS tumors.

Question 35Question →

A 9-year-old boy is admitted to the pediatric oncology unit with newly diagnosed T-cell acute lymphoblastic leukemia. He has a 2-week history of worsening fatigue, bone pain, and shortness of breath. Chest radiograph shows a large anterior mediastinal mass. Before the initiation of induction chemotherapy, laboratory studies are obtained:

Laboratory Test	Result	Reference Range
Leukocyte count	$165,000/\text{mm}^3$	$4,500-11,000/\text{mm}^3$
Hemoglobin	$8.4\text{ g/dL}$	$11.5-15.5\text{ g/dL}$
Platelet count	$48,000/\text{mm}^3$	$150,000-400,000/\text{mm}^3$
Blood urea nitrogen	$38\text{ mg/dL}$	$7-20\text{ mg/dL}$
Creatinine	$1.6\text{ mg/dL}$	$0.3-0.7\text{ mg/dL}$
Uric acid	$12.4\text{ mg/dL}$	$2.0-5.5\text{ mg/dL}$
Calcium	$7.4\text{ mg/dL}$	$8.8-10.8\text{ mg/dL}$
Phosphorus	$7.2\text{ mg/dL}$	$3.0-5.4\text{ mg/dL}$
Potassium	$4.8\text{ mEq/L}$	$3.4-4.7\text{ mEq/L}$
Lactate dehydrogenase	$5,200\text{ U/L}$	$120-300\text{ U/L}$

An electrocardiogram shows normal sinus rhythm with no ST-segment or T-wave abnormalities. The patient does not exhibit tetany or seizures. Vigorous intravenous hydration with normal saline is initiated.

Which of the following is the most appropriate additional pharmacologic intervention for this patient's metabolic derangements?

Intravenous rasburicase

Intravenous allopurinol

Intravenous sodium bicarbonate

Intravenous calcium gluconate

Oral sevelamer

Show answer & explanation

Answer: Intravenous rasburicase

Answer

The most appropriate intervention is to administer intravenous rasburicase to rapidly degrade the severely elevated uric acid.

The correct answer is intravenous rasburicase. This patient presents with spontaneous tumor lysis syndrome (TLS) secondary to T-cell acute lymphoblastic leukemia. TLS is characterized by the massive release of intracellular contents, leading to hyperkalemia, hyperphosphatemia, hyperuricemia, and secondary hypocalcemia. This patient has extremely high-risk features (leukocyte count

>100,000/\text{mm}^3

and significantly elevated LDH) and has already developed acute kidney injury (AKI) from uric acid nephropathy (creatinine

1.6\text{ mg/dL}

, uric acid

12.4\text{ mg/dL}

). In this scenario, aggressive intravenous hydration combined with rasburicase is the standard of care. Rasburicase is a recombinant urate oxidase enzyme that rapidly catalyzes the conversion of existing poorly soluble uric acid into allantoin, an inactive and highly water-soluble metabolite that is easily excreted. This rapid clearance of uric acid is necessary to reverse the AKI.

Step-by-Step Solution

Identify the clinical syndrome

The patient has spontaneous tumor lysis syndrome (TLS).

High tumor burden (WBC 165,000/mm³, huge mediastinal mass, LDH 5,200 U/L) has led to the release of intracellular contents, resulting in hyperuricemia, hyperphosphatemia, and secondary hypocalcemia prior to treatment.

Assess the severity and organ function

The patient has established acute kidney injury (creatinine 1.6 mg/dL).

The severe uric acid level of 12.4 mg/dL has likely caused urate crystal precipitation in the renal tubules, leading to an acute decline in kidney function.

Select the appropriate pharmacologic therapy

Intravenous rasburicase is required.

Because the patient already has severe hyperuricemia and AKI, preventing new uric acid formation (with allopurinol) is insufficient. Rasburicase degrades pre-existing uric acid into highly soluble allantoin, rapidly clearing it from the serum and protecting the kidneys.

Key Concept

In patients with high-risk tumor lysis syndrome and established hyperuricemia or acute kidney injury, rasburicase is indicated over allopurinol because it rapidly degrades existing uric acid into soluble allantoin.

Estimated Time:1m 30s

Question 36Question →

A 14-year-old boy is brought to the emergency department by his parents due to a 1-week history of progressively worsening shortness of breath, a barking cough, and facial swelling. On physical examination, the patient is anxious, diaphoretic, and leaning forward in a seated position. He is using accessory muscles of respiration. Vital signs show a temperature of 37.8°C (100.0°F), heart rate of 135/min, respiratory rate of 32/min, and oxygen saturation of 91% on room air. Inspection reveals distended neck veins and facial plethora. A portable chest radiograph demonstrates a massive anterior mediastinal mass causing significant tracheal deviation and compression. You are concerned for superior mediastinal syndrome with severe airway compromise.

Arrange the following management steps in the most appropriate sequential order to safely stabilize and diagnose this patient.

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Answer

The correct sequence is: 1) Maintain the patient in an awake, upright position with supplemental oxygen. 2) Attempt minimally invasive diagnostic sampling under local anesthesia. 3) Administer empiric cytoreductive therapy if the airway is critically compromised and minimally invasive tests are inadequate. 4) Perform definitive surgical biopsy under general anesthesia once the airway is secure.

The management of an anterior mediastinal mass with airway compromise requires a careful balance between obtaining a diagnostic sample and preventing fatal airway collapse. The immediate priority is maintaining the patient's spontaneous respiratory drive by keeping them awake, upright, and on supplemental oxygen. General anesthesia and positive pressure ventilation can precipitate complete airway obstruction due to the loss of negative intrathoracic pressure. Therefore, initial diagnostic efforts must focus on minimally invasive procedures that require only local anesthesia (e.g., peripheral blood flow cytometry, thoracentesis, or superficial lymph node biopsy). If these methods are unyielding and the patient is in imminent danger of respiratory failure, empiric cytoreductive therapy (e.g., corticosteroids or radiation) is indicated as a life-saving measure to shrink the mass, despite the risk of obscuring the histologic diagnosis. Only after the mass has responded to empiric therapy and the airway is secure can a definitive biopsy be safely performed under general anesthesia.

Step-by-Step Solution

Identify the critical nature of the patient's presentation.

The patient has superior mediastinal syndrome and severe tracheal compression.

Maintaining the patient's spontaneous respiratory drive and negative intrathoracic pressure is essential to prevent complete airway collapse.

Prioritize initial stabilization without the use of sedation.

Select maintaining the patient in an awake, upright position with supplemental oxygen as the first step.

Sedatives or general anesthesia abolish chest wall muscle tone and bronchial smooth muscle tension, which can quickly lead to fatal airway obstruction in this setting.

Determine the safest initial method for obtaining a tissue diagnosis.

Select minimally invasive sampling (e.g., peripheral blood flow cytometry) as the second step.

Diagnosis must be attempted via methods that do not require sedation or general anesthesia to protect the airway.

Decide on the appropriate action if non-invasive diagnostics fail and the patient clinically deteriorates.

Select empiric cytoreductive therapy (e.g., corticosteroids) as the third step.

Although empiric steroids alter tumor histology, they are a necessary life-saving measure to shrink the tumor if airway collapse is imminent and diagnosis is delayed.

Plan for definitive diagnosis once the patient is no longer in acute distress.

Select surgical tissue biopsy under general anesthesia as the final step.

Once the tumor burden has been sufficiently reduced and the airway is safe, general anesthesia can be induced to perform a definitive biopsy if the diagnosis remains unknown.

Key Concept

Management of anterior mediastinal mass with airway compromise

Question 37Question →

An $11$ -month-old male infant is brought to the pediatric hematology clinic for a follow-up evaluation of thrombocytopenia. He has a history of recurrent acute otitis media and a recent hospitalization for pneumococcal pneumonia. His mother reports that he has been pulling himself to a stand and cruising along furniture for the past month. Physical examination reveals scattered petechiae over the lower extremities and intensely pruritic, erythematous, scaly plaques in the flexural creases of his arms and legs. Laboratory evaluation shows:

- Hemoglobin: $10.5 \text{ g/dL}$
- White blood cell count: $6,800/\text{mm}^3$ (Normal differential)
- Platelet count: $28,000/\text{mm}^3$
- Mean platelet volume (MPV): $5.5 \text{ fL}$ (Reference range: $7.5 - 11.5 \text{ fL}$ )

A genetic test confirms a mutation in a gene responsible for actin cytoskeleton reorganization. Which of the following is the most appropriate management for this patient?

Referral for human leukocyte antigen typing and hematopoietic stem cell transplantation

Administration of live-attenuated viral vaccines to protect against systemic infections

Initiation of empiric continuous therapy with broad-spectrum intravenous antibiotics

Reassurance that the cutaneous findings represent a transient, benign dermatologic condition

Referral for a comprehensive neurologic evaluation due to significant gross motor delay

Show answer & explanation

Answer: Referral for human leukocyte antigen typing and hematopoietic stem cell transplantation

Answer

Referral for human leukocyte antigen typing and hematopoietic stem cell transplantation

Wiskott-Aldrich syndrome (WAS) is an X-linked recessive immunodeficiency disorder caused by a mutation in the WAS gene, which leads to impaired actin cytoskeleton reorganization in white blood cells and platelets. It classically presents in male infants with a triad of microthrombocytopenia (low platelet count and profoundly decreased mean platelet volume), eczema, and recurrent infections. Because of the severe combined B-cell and T-cell dysfunction, patients are at extremely high risk for life-threatening infections, severe hemorrhage, and subsequent hematologic malignancies. The only definitive, curative treatment for WAS is hematopoietic stem cell transplantation (HSCT). Therefore, early referral for human leukocyte antigen (HLA) typing and subsequent HSCT is the most appropriate long-term management.

Step-by-Step Solution

Analyze the clinical presentation and laboratory findings.

The patient is an infant male presenting with recurrent infections, a pruritic flexural rash (eczema), and profound thrombocytopenia with unusually small platelets (low mean platelet volume).

Synthesizing these specific findings is essential to establish the underlying diagnosis before determining management.

Identify the specific underlying syndrome.

The classic triad of microthrombocytopenia, eczema, and recurrent infections, combined with an actin cytoskeleton defect, is diagnostic of Wiskott-Aldrich syndrome (WAS).

Recognizing the WAS triad and the significance of the low MPV distinguishes this genetic disorder from other causes of childhood thrombocytopenia, such as immune thrombocytopenia (ITP).

Determine the definitive long-term management for the diagnosed condition.

Because WAS involves severe combined immunodeficiency and high risk for hematologic malignancies, the only curative therapy is hematopoietic stem cell transplantation (HSCT).

While supportive care includes prophylactic antibiotics and IVIG, HSCT is required to restore normal immune and platelet function and prevent early mortality.

Key Concept

Wiskott-Aldrich syndrome is characterized by the triad of microthrombocytopenia (low MPV), eczema, and recurrent infections; the only definitive, curative treatment is hematopoietic stem cell transplantation.

Question 38Question →

A pediatric oncology clinic evaluates four children and adolescents with newly diagnosed malignancies. Based on their clinical presentation and initial diagnostic findings, match each patient to the most characteristic underlying genetic or molecular abnormality.

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Answer

The rapidly expanding maxillary mass with macrophages matches t(8;14) (Burkitt lymphoma). The B-ALL with a favorable prognosis matches t(12;21). The diaphyseal femur lesion with CD99+ cells matches t(11;22) (Ewing sarcoma). The abdominal mass with elevated catecholamines matches MYCN amplification (neuroblastoma).

Each pediatric malignancy has a highly stereotyped clinical presentation that correlates precisely with specific molecular and genetic drivers. Burkitt lymphoma requires the t(8;14) c-myc translocation for its explosive growth. Favorable pediatric B-ALL is driven by the t(12;21) ETV6-RUNX1 fusion. Ewing sarcoma relies on the t(11;22) EWS-FLI1 fusion product. Neuroblastoma aggression is closely tied to MYCN amplification.

Step-by-Step Solution

Analyze the 15-year-old boy's presentation.

Identified as Burkitt lymphoma based on the jaw/maxillary mass, high proliferative index, and 'starry sky' macrophages. Matches with t(8;14) causing c-myc overexpression.

Burkitt lymphoma is classically associated with Epstein-Barr virus in endemic cases and universally driven by c-myc dysregulation.

Analyze the 4-year-old girl's presentation.

Identified as pediatric B-cell ALL. The favorable prognostic translocation is t(12;21).

Cytogenetics are critical for ALL risk stratification; t(12;21) is a classic favorable marker, whereas t(9;22) or t(4;11) would be unfavorable.

Analyze the 13-year-old boy's presentation.

Identified as Ewing sarcoma based on the lytic diaphyseal bone lesion and CD99+ small round blue cells. Matches with t(11;22).

Ewing sarcoma is distinctly driven by the EWS-FLI1 fusion product from the t(11;22) translocation.

Analyze the 2-year-old boy's presentation.

Identified as neuroblastoma based on the midline-crossing abdominal mass, opsoclonus-myoclonus, and elevated VMA/HVA. Matches with MYCN (N-myc) amplification.

Neuroblastoma originates from sympathetic ganglion cells and its biologic behavior is strongly correlated with the presence of MYCN amplification.

Key Concept

Clinical and molecular correlations of pediatric malignancies

Question 39Question →

A 6-year-old girl is evaluated in the emergency department due to a 2-day history of progressively worsening back pain and new-onset difficulty walking. She has not voided urine for the past 14 hours. The patient was diagnosed with stage IV neuroblastoma 8 months ago and is currently receiving systemic chemotherapy. Temperature is 37.0°C (98.6°F), heart rate is 112/min, and blood pressure is 108/68 mm Hg. Physical examination reveals 3/5 muscle strength in bilateral lower extremities, patellar hyperreflexia, and decreased sensation to pinprick below the umbilicus. A palpable, distended bladder is noted. Suspecting an acute oncologic emergency, arrange the following management steps in the most appropriate chronological order from first to last.

Drag items to arrange them in the correct order

Show answer & explanation

Answer

The correct sequence of management for suspected malignant spinal cord compression is to first administer intravenous dexamethasone, followed by obtaining an urgent MRI of the entire spine, performing localized spinal decompression, and finally modifying the systemic chemotherapy regimen.

Malignant spinal cord compression (MSCC) is a severe oncologic emergency characterized by back pain, motor weakness, sensory deficits (e.g., a distinct sensory level), and autonomic dysfunction (e.g., urinary retention). In a pediatric patient with a known solid tumor (such as neuroblastoma or sarcoma) presenting with signs of MSCC, the absolute first step in management is the administration of high-dose corticosteroids, such as intravenous dexamethasone. Corticosteroids decrease vasogenic edema, quickly reduce pressure on the spinal cord, and represent the most critical intervention to prevent irreversible ischemia and preserve neurologic function. They must be administered immediately upon clinical suspicion, prior to definitive imaging. Once steroids are given, an urgent MRI of the entire spine should be obtained to confirm the diagnosis, locate the exact level of compression, and identify any additional asymptomatic epidural metastases (which occur in a significant percentage of patients). After the anatomy is clearly defined, definitive local decompression is performed via neurosurgery (e.g., laminectomy) or radiation therapy, depending on tumor radiosensitivity and spinal stability. Finally, once the acute emergency is resolved, the patient's systemic chemotherapy regimen can be modified by the oncology team for long-term disease management.

Step-by-Step Solution

Administer intravenous dexamethasone

Rapid reduction of peritumoral vasogenic edema.

Protects the spinal cord from further ischemic injury and preserves neurologic function; must be given empirically before imaging.

Obtain an urgent MRI of the entire spine

Confirmation of epidural metastasis and mapping of disease extent.

Required to determine the exact level of cord compression and to identify any synchronous asymptomatic lesions to guide definitive local therapy.

Perform localized spinal decompression

Relief of physical pressure on the spinal cord.

Surgical resection or radiation therapy provides definitive local control based on the precise anatomical findings from the MRI.

Modify the tumor-specific systemic chemotherapy regimen

Targeted treatment of the underlying neuroblastoma progression.

Addresses the systemic disease once the acute local threat to neurologic function is neutralized.

Key Concept

Malignant spinal cord compression requires immediate empiric administration of high-dose corticosteroids to preserve neurologic function prior to obtaining definitive imaging.

Question 40Question →

During a routine health maintenance visit, the parents of a $4$ -year-old girl inquire about her eligibility for required preschool immunizations. The patient was diagnosed with standard-risk acute lymphoblastic leukemia (ALL) two years ago. She successfully completed induction and consolidation therapy and is currently in the maintenance phase of her treatment, taking daily oral mercaptopurine and weekly oral methotrexate. She has been feeling well, with no recent fevers, weight loss, or respiratory symptoms. Her temperature is $37.0^\circ\text{C}$ ( $98.6^\circ\text{F}$ ), blood pressure is $95/60\text{ mmHg}$ , and heart rate is $90/\text{min}$ . Physical examination reveals a well-appearing, active child with no lymphadenopathy or hepatosplenomegaly.

Laboratory evaluation shows:
Hemoglobin: $11.5\text{ g/dL}$
Leukocyte count: $4,500/\mu\text{L}$
Absolute neutrophil count: $1,800/\mu\text{L}$
Platelet count: $250,000/\mu\text{L}$

A review of her immunization record indicates that she received all scheduled vaccines during her first year of life but has not yet received her $4$ - to $6$ -year booster series, which includes the diphtheria, tetanus, and acellular pertussis (DTaP), inactivated poliovirus (IPV), measles, mumps, and rubella (MMR), and varicella vaccines.

Which of the following is the most appropriate next step in management regarding her immunizations?

Administer the DTaP and IPV vaccines today, but withhold the MMR and varicella vaccines until at least

3

months after chemotherapy is completed

Administer the DTaP, IPV, MMR, and varicella vaccines today to ensure full preschool requirements are met

Withhold all vaccines today because her laboratory results indicate severe neutropenia

Administer the DTaP, IPV, MMR, and varicella vaccines today because her current medications do not contraindicate their use

Withhold all vaccines today because all immunizations are universally contraindicated during active chemotherapy regimens

Show answer & explanation

Answer: Administer the DTaP and IPV vaccines today, but withhold the MMR and varicella vaccines until at least $3$ months after chemotherapy is completed

Answer

The correct approach is to administer the inactivated vaccines (DTaP and IPV) while withholding the live-attenuated vaccines (MMR and varicella).

The correct answer identifies that the patient is currently on maintenance chemotherapy (mercaptopurine and methotrexate) for acute lymphoblastic leukemia, which induces systemic immunosuppression. In immunocompromised patients, inactivated vaccines (such as DTaP and IPV) are safe, cannot replicate, and should be administered according to the standard schedule to provide protection, even though the immune response may be somewhat blunted. Conversely, live-attenuated vaccines (such as MMR and varicella) are strictly contraindicated during active chemotherapy and for a minimum of

3

months after its completion. Administration of live vaccines to this patient carries a high risk of vaccine-strain viral replication and disseminated disease.

Step-by-Step Solution

Determine the patient's immune status based on her current medical history and medications.

The patient is on mercaptopurine and methotrexate for ALL maintenance therapy, meaning she is actively immunosuppressed.

Immunosuppression dictates which categories of vaccines can be safely administered.

Evaluate the laboratory results for acute contraindications.

The absolute neutrophil count (

1,800/\mu\text{L}

) and other counts are adequate, ruling out severe neutropenia as an acute barrier to routine care.

Severe cytopenias or acute acute illness might temporarily delay even inactivated vaccines, but this patient is stable.

Categorize the requested vaccines into live-attenuated versus inactivated.

DTaP and IPV are inactivated (toxoid/killed); MMR and varicella are live-attenuated.

Live-attenuated vaccines can cause unchecked clinical infection in immunocompromised hosts.

Apply the ACIP/AAP immunization guidelines for pediatric oncology patients.

Administer inactivated vaccines (DTaP, IPV) safely today. Delay live vaccines (MMR, varicella) until cellular immunity recovers.

Guidelines explicitly state live vaccines are contraindicated during chemotherapy and for at least

3

months following its completion.

Key Concept

Immunization guidelines in pediatric oncology patients receiving chemotherapy

Estimated Time:1m 0s

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Pediatric Hematology and Oncology

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