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A 61-year-old man with a history of uncontrolled hypertension and a 40-pack-year smoking history is brought to the emergency department for sudden-onset, severe chest pain. He describes the pain as sharp, excruciating, and radiating directly to the space between his shoulder blades. He appears diaphoretic and in acute distress. Vital signs show a heart rate of 110/min, respiratory rate of 22/min, and blood pressure of 185/105 mmHg in the right arm and 135/85 mmHg in the left arm. Physical examination reveals an early diastolic decrescendo murmur auscultated at the right upper sternal border. An electrocardiogram reveals sinus tachycardia with non-specific ST-segment changes.

Arrange the following differential diagnoses in order from the MOST likely (highest pre-test probability) to the LEAST likely, based on this patient's clinical presentation.

Drag items to arrange them in the correct order

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Answer

The correct order from most to least likely is: Acute aortic dissection, Acute myocardial infarction, Pulmonary embolism, Esophageal perforation, and Acute pericarditis.

The correct sequence prioritizes the diagnoses based on how completely they explain the entire clinical presentation. Acute aortic dissection is the only diagnosis that accounts for the severe pain radiating to the back, the asymmetric blood pressures (due to extension into the brachiocephalic or subclavian arteries), and the new aortic regurgitation murmur (due to retrograde extension into the aortic root). Acute myocardial infarction is the next most plausible given the patient's immense risk factors, followed by pulmonary embolism. Esophageal perforation and acute pericarditis lack necessary historical triggers (such as retching) and classic exam findings (such as a friction rub), making them the least likely considerations.

Step-by-Step Solution

Analyze the history and physical examination findings.

Identified a 61-year-old male with severe chest pain radiating to the back, highly asymmetric upper extremity blood pressures (185/105 vs 135/85), and a new early diastolic decrescendo murmur.

Extracting key distinguishing clinical features is the essential first step in formulating an accurate differential diagnosis.

Determine the single most likely diagnosis based on the integrated clinical picture.

Acute aortic dissection is prioritized first.

The triad of pain radiating to the back, pulse/blood pressure deficits, and an acute aortic regurgitation murmur perfectly aligns with an ascending aortic dissection.

Rank the remaining life-threatening cardiovascular and pulmonary conditions.

Acute myocardial infarction is ranked second, followed by pulmonary embolism.

Myocardial infarction is a very common cause of severe chest pain in patients with vascular risk factors but lacks definitive electrocardiogram evidence here and does not explain the blood pressure gap. Pulmonary embolism can cause sudden pain and tachycardia but lacks pleuritic features in this presentation.

Rank the less likely non-vascular and inflammatory etiologies.

Esophageal perforation is ranked fourth, and acute pericarditis is ranked fifth.

Esophageal perforation lacks the classic antecedent retching. Pericarditis is least likely because the pain is not described as pleuritic or positional, and there is no pericardial friction rub.

Key Concept

Formulating a differential diagnosis for acute severe chest pain requires synthesizing specific distinguishing physical examination findings, such as pulse deficits and new murmurs, to prioritize potentially lethal etiologies.

Question 4422Question →

A 29-year-old man is evaluated in the intensive care unit due to sudden-onset hemodynamic instability. He was admitted two days prior for acute respiratory distress syndrome secondary to severe bacterial pneumonia. He is currently intubated and receiving pressure-controlled mechanical ventilation with high positive end-expiratory pressure. A nurse calls the physician to the bedside after the ventilator begins alarming for consistently high peak airway pressures. Current vital signs show a blood pressure of 72/40 mm Hg, a heart rate of 145/min, and an oxygen saturation of 82% despite an $FiO_2$ of $1.0$ . Physical examination reveals absent breath sounds over the right hemithorax, hyperresonance to percussion on the right side, and prominently distended jugular veins. The trachea appears deviated to the left. Which of the following is the single most urgent initial step in the stabilization of this patient?

Immediate right-sided needle or finger thoracostomy

Urgent portable chest radiography

Rapid administration of a 1-liter intravenous crystalloid bolus

Administration of broad-spectrum intravenous antibiotics

Obtaining an arterial blood gas sample for analysis

Show answer & explanation

Answer: Immediate right-sided needle or finger thoracostomy

Answer

Immediate right-sided needle or finger thoracostomy

The correct answer is immediate right-sided needle or finger thoracostomy. This patient, who is receiving positive-pressure ventilation for acute respiratory distress syndrome, has suddenly developed a right-sided tension pneumothorax (indicated by absent right-sided breath sounds, hyperresonance, high peak airway pressures, leftward tracheal deviation, and obstructive shock with jugular venous distention). Tension pneumothorax is a clinical diagnosis, and when a patient is hemodynamically unstable, the primary treatment is immediate decompression of the pleural space. This rapidly restores venous return and cardiac output. Waiting for imaging or performing other tasks first is contraindicated.

Step-by-Step Solution

Analyze the patient's vital signs and physical exam findings.

The patient has severe hypotension, tachycardia, hypoxia, unilaterally absent breath sounds, hyperresonance, jugular venous distention, and tracheal deviation.

These findings in a patient on positive-pressure ventilation point precisely to a clinical diagnosis of tension pneumothorax.

Determine the pathophysiological mechanism of the patient's shock.

The tension pneumothorax is causing obstructive shock by compressing the superior and inferior vena cava, severely reducing venous return and cardiac output.

Understanding that this is obstructive shock dictates that the mechanical obstruction must be relieved immediately.

Select the most appropriate immediate intervention.

Immediate needle decompression or finger thoracostomy must be performed on the right side.

Tension pneumothorax is a clinical diagnosis; treatment must precede diagnostic imaging to prevent cardiac arrest.

Key Concept

Clinical diagnosis and immediate empiric decompression of tension pneumothorax in mechanically ventilated patients.

Question 4423Question →

A $28$ -year-old woman is brought to the emergency department by her roommate due to confusion, nausea, and ringing in her ears for the past $6$ hours. She has a history of major depressive disorder and was recently prescribed a new medication for chronic lower back pain. Vital signs show a temperature of $37.8^\circ$ C ( $100.0^\circ$ F), blood pressure of $110/70$ mmHg, pulse of $115$ /min, and respiratory rate of $28$ /min. Physical examination reveals a diaphoretic and anxious woman.

Laboratory studies are obtained:

Complete Blood Count & Serum Chemistry	Result	Reference Range
Hemoglobin	$13.2$ g/dL	$12.0$ – $16.0$ g/dL
Platelets	$210,000/\mu$ L	$150,000$ – $400,000/\mu$ L
Sodium ( $Na^+$ )	$140$ mEq/L	$136$ – $145$ mEq/L
Potassium ( $K^+$ )	$3.8$ mEq/L	$3.5$ – $5.0$ mEq/L
Chloride ( $Cl^-$ )	$104$ mEq/L	$98$ – $106$ mEq/L
Bicarbonate ( $HCO_3^-$ )	$14$ mEq/L	$22$ – $28$ mEq/L
Blood urea nitrogen	$18$ mg/dL	$7$ – $18$ mg/dL
Creatinine	$0.9$ mg/dL	$0.6$ – $1.2$ mg/dL

Arterial Blood Gas (Room Air)	Result	Reference Range
pH	$7.47$	$7.35$ – $7.45$
$PaCO_2$	$20$ mm Hg	$35$ – $45$ mm Hg
$PaO_2$	$98$ mm Hg	$80$ – $100$ mm Hg

Which of the following is the most accurate interpretation of this patient's acid-base status?

Mixed primary high anion gap metabolic acidosis and primary respiratory alkalosis

Primary respiratory alkalosis with appropriate metabolic compensation

Primary high anion gap metabolic acidosis with appropriate respiratory compensation

Mixed primary normal anion gap metabolic acidosis and primary respiratory alkalosis

Mixed primary high anion gap metabolic acidosis and primary metabolic alkalosis

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Answer: Mixed primary high anion gap metabolic acidosis and primary respiratory alkalosis

Answer

The correct interpretation is a mixed primary high anion gap metabolic acidosis and primary respiratory alkalosis.

The patient's presentation of tinnitus, tachypnea, diaphoresis, and confusion is highly characteristic of acute salicylate toxicity. Laboratory interpretation requires a step-wise approach. First, the arterial pH is 7.47 (alkalemia) driven by a low PaCO2 of 20 mm Hg, confirming a primary respiratory alkalosis resulting from direct stimulation of the medullary respiratory center. Second, the serum anion gap must be calculated: 140 - (104 + 14) = 22 mEq/L. This elevated gap indicates an accumulation of unmeasured organic acids, establishing an independent primary high anion gap metabolic acidosis (HAGMA). Finally, checking Winter's formula (1.5 * 14 + 8 = 29 mm Hg) demonstrates that the actual PaCO2 (20 mm Hg) is much lower than the expected compensatory range (27-31 mm Hg), conclusively proving this is a mixed primary disorder.

Step-by-Step Solution

Identify the primary acid-base disturbance by evaluating the pH and PaCO2.

The pH is 7.47 (alkalemia) and the PaCO2 is 20 mm Hg (hypocapnia). Because the low PaCO2 drives the pH in the alkaline direction, a primary respiratory alkalosis is present.

Establishing the primary driver is the essential first step in acid-base interpretation.

Calculate the serum anion gap to check for an underlying metabolic acidosis.

AG = Na - (Cl + HCO3) = 140 - (104 + 14) = 22 mEq/L. Since 22 > 12, a high anion gap metabolic acidosis is also present.

An elevated anion gap reveals an accumulation of unmeasured acids (e.g., salicylic acid, lactic acid), which represents an independent primary metabolic disorder regardless of the pH.

Apply Winter's formula to determine if the respiratory alkalosis is purely compensatory or a separate primary disorder.

Expected PaCO2 = 1.5 * HCO3 + 8 = 1.5 * 14 + 8 = 29 +/- 2 mm Hg. The actual PaCO2 (20 mm Hg) is significantly lower than the expected compensatory range.

A PaCO2 lower than the predicted compensatory level confirms the simultaneous presence of an independent primary respiratory alkalosis, solidifying the diagnosis of a mixed acid-base disorder.

Key Concept

Patients with severe salicylate toxicity typically present with a mixed primary acid-base disorder: a primary respiratory alkalosis (due to direct medullary respiratory center stimulation) and a primary high anion gap metabolic acidosis (due to uncoupling of oxidative phosphorylation and accumulation of organic acids).

Alternative Method

Instead of Winter's formula, the Delta Ratio (Change in AG / Change in HCO3) can be evaluated. A ratio around 1.0 (10 / 10 in this case) confirms a pure high anion gap metabolic acidosis component. However, the simultaneous severe alkalemia (pH 7.47) and profound hypocapnia independently mandate the diagnosis of a concurrent primary respiratory alkalosis.

Estimated Time:2m 0s

Question 4424Question →

A 74-year-old retired accountant is accompanied to the geriatrics clinic by his son. The family is concerned because the patient has been repeatedly misplacing household items, forgetting recent conversations, and recently got lost while driving a familiar route to the grocery store. These changes have evolved gradually over the past 14 months. The patient feels fine and dismisses the concerns, attributing them to normal aging. Medical history is significant for well-controlled type 2 diabetes mellitus and osteoarthritis. Vital signs are within normal limits. General physical and detailed neurological examinations show no focal deficits, resting tremors, or gait abnormalities. His score on the Montreal Cognitive Assessment is 20/30, with prominent point deductions on delayed recall and visuospatial tasks. Which of the following diagnostic investigations should be ordered concurrently as part of the initial routine evaluation for this patient's cognitive decline? (Select all that apply)

Select all that apply

Serum vitamin B12 level

Serum thyroid-stimulating hormone (TSH) level

Magnetic resonance imaging (MRI) of the brain

Fluorodeoxyglucose-positron emission tomography (FDG-PET) of the brain

Cerebrospinal fluid analysis for tau and amyloid-beta proteins

Show answer & explanation

Answer: Serum vitamin B12 level; Serum thyroid-stimulating hormone (TSH) level; Magnetic resonance imaging (MRI) of the brain

Answer

The initial routine diagnostic workup for new-onset cognitive impairment should concurrently include a serum vitamin B12 level, a serum thyroid-stimulating hormone (TSH) level, and structural neuroimaging (such as an MRI of the brain).

In the initial evaluation of any patient presenting with cognitive impairment and suspected dementia, standard of care mandates ruling out reversible, metabolic, and structural etiologies. This core battery of tests concurrently includes serum vitamin B12, thyroid-stimulating hormone (TSH), and structural brain imaging (with MRI being preferred over CT due to higher sensitivity for cerebrovascular disease and regional atrophy). Addressing abnormalities in B12 or TSH can halt or reverse cognitive decline, while an MRI rules out potentially treatable structural causes such as subdural hematomas, normal pressure hydrocephalus, or tumors.

Step-by-Step Solution

Identify the primary clinical syndrome from the patient's history and objective findings.

The patient has a 14-month history of progressive memory loss and functional impairment (getting lost) with a Montreal Cognitive Assessment score of 20/30, establishing a major neurocognitive disorder (dementia).

Confirming the presence of cognitive decline dictates the need for a comprehensive diagnostic evaluation.

Determine the standard goals of the initial diagnostic workup for dementia.

The primary goal is to identify common, potentially reversible causes of cognitive decline and rule out occult structural brain lesions.

A small but significant percentage of dementia cases are partially or fully reversible if an underlying metabolic, endocrine, or structural abnormality is addressed.

Select the guideline-recommended concurrent baseline tests.

Standard guidelines require checking vitamin B12 and TSH levels, along with obtaining a structural neuroimaging study (MRI or non-contrast CT of the brain).

These tests efficiently and safely screen for thyroid dysfunction, vitamin deficiencies, and structural pathology (e.g., strokes, tumors, normal pressure hydrocephalus) without exposing the patient to unnecessary radiation or invasive procedures prematurely.

Key Concept

The initial diagnostic evaluation of a patient with suspected dementia must include screening for reversible causes (using TSH and vitamin B12 levels) and structural neuroimaging (MRI or non-contrast CT of the brain) to rule out mass lesions or cerebrovascular disease.

Question 4425Question →

During a scheduled health maintenance visit, a 24-year-old male college student is evaluated. He reports feeling well and has no acute complaints. Two weeks ago, he underwent an emergency splenectomy following a severe mountain biking accident that caused massive splenic rupture. His postoperative recovery has been uncomplicated. He has no other medical conditions and takes no daily medications. He does not smoke, drink alcohol, or use illicit drugs. Review of his immunization records shows that he completed all standard childhood vaccinations, including a single dose of the quadrivalent meningococcal conjugate vaccine (MenACWY) and the tetanus, diphtheria, and acellular pertussis (Tdap) vaccine at age 11. He has not received any vaccines since that time.

Based on current Advisory Committee on Immunization Practices (ACIP) guidelines, administration of which of the following vaccine regimens is the most appropriate next step for this patient today?

Administer MenACWY and serogroup B meningococcal vaccines only, to target the most common post-splenectomy pathogens.

Administer 20-valent pneumococcal conjugate and Tdap vaccines only, as additional immunizations are not indicated.

Administer 20-valent pneumococcal conjugate, MenACWY, serogroup B meningococcal, Haemophilus influenzae type b, and Tdap vaccines.

Administer 23-valent pneumococcal polysaccharide, serogroup B meningococcal, and Haemophilus influenzae type b vaccines.

Defer all immunizations for at least 3 months postoperatively to allow for adequate immune system recovery.

Show answer & explanation

Answer: Administer 20-valent pneumococcal conjugate, MenACWY, serogroup B meningococcal, Haemophilus influenzae type b, and Tdap vaccines.

Answer

The most appropriate approach is to administer the 20-valent pneumococcal conjugate vaccine, the MenACWY booster, the serogroup B meningococcal vaccine, the Haemophilus influenzae type b vaccine, and a Tdap booster.

Patients with anatomic or functional asplenia are at severe risk for overwhelming post-splenectomy infection (OPSI), primarily driven by encapsulated organisms: Streptococcus pneumoniae, Neisseria meningitidis, and Haemophilus influenzae type b (Hib). According to current ACIP guidelines, these patients require comprehensive vaccination against all three pathogens. For pneumococcal coverage, adults with asplenia who have not previously received a conjugate vaccine should receive a single dose of PCV20 (or alternatively, PCV15 followed by PPSV23). For meningococcal coverage, they require both the MenACWY vaccine (a booster is needed here since his initial dose was more than 5 years ago) and the initiation of the MenB vaccine series. A single dose of the Hib vaccine is also strongly indicated for asplenic adults who were not vaccinated in adulthood. Furthermore, because the patient's last Tdap was at age 11 (13 years ago), a routine 10-year booster is indicated today. Timing is critical; for emergency splenectomies, vaccines should be administered at least 14 days postoperatively to ensure an optimal immune response without unnecessarily delaying protection, making today the ideal time for administration.

Step-by-Step Solution

Identify the patient's immunocompromised state and the associated risk profile.

The patient is 14 days post-emergency splenectomy, resulting in anatomic asplenia. He is at severe risk for overwhelming post-splenectomy infection (OPSI) caused by encapsulated organisms.

The spleen plays a critical role in the opsonization and phagocytic clearance of encapsulated bacteria from the bloodstream.

Determine the optimal timing for immunization.

Vaccines should be administered today.

For emergency splenectomies, current guidelines recommend administering indicated vaccines at least 14 days postoperatively. This allows the immune system to recover sufficiently from surgical stress to mount an adequate antibody response.

Identify the specific pathogens that require targeted vaccination.

The patient requires protection against Streptococcus pneumoniae, Neisseria meningitidis, and Haemophilus influenzae type b.

These three pathogens are the primary encapsulated bacteria responsible for rapid, fatal sepsis in asplenic patients.

Select the exact vaccine formulations required by ACIP guidelines for an unimmunized adult asplenic patient.

The indicated regimen includes PCV20 (pneumococcal), MenACWY (booster, as his last dose was >5 years ago), MenB (primary series), Hib (single dose for unimmunized asplenic adults), and Tdap (routine booster, as his last dose was >10 years ago).

This combination comprehensively fulfills the 2026 evidence-based recommendations for maximizing post-splenectomy immunity.

Key Concept

Adults with anatomic or functional asplenia require targeted vaccination against encapsulated organisms (S. pneumoniae, N. meningitidis, H. influenzae) administered at least 14 days following an emergency splenectomy.

Question 4426Question →

A 38-year-old man comes to the outpatient clinic reporting a one-year history of worsening joint pain, excessive sweating, and frequent headaches. He mentions that he recently had to have his wedding band resized because it would no longer fit his finger. He has no significant past medical history and takes no medications. Vital signs show a blood pressure of 152/95 mmHg, heart rate of 78/min, and respiratory rate of 14/min. Physical examination reveals coarse facial features, a prominent jaw, and widening of the spaces between the lower incisors. His hands and feet appear enlarged with thickened skin. Which of the following is the most appropriate next step in the diagnostic workup?

Measurement of serum insulin-like growth factor 1 concentration

Measurement of serum growth hormone following an oral glucose load

Magnetic resonance imaging of the brain with contrast

Measurement of a random serum growth hormone concentration

Initiation of a nonsteroidal anti-inflammatory drug and routine follow-up

Show answer & explanation

Answer: Measurement of serum insulin-like growth factor 1 concentration

Answer

Measurement of serum insulin-like growth factor 1 concentration

The correct next step is the measurement of serum insulin-like growth factor 1 (IGF-1) concentration. This patient's presentation of acral enlargement (needing a ring resized, enlarged hands and feet), coarse facial features, widening of the teeth, excessive sweating, and hypertension is the classic clinical picture of acromegaly. Acromegaly is typically caused by a growth hormone (GH)-secreting pituitary adenoma. Because GH is secreted in a pulsatile manner and has a short half-life, random serum GH levels fluctuate widely and are unreliable for diagnosis. Instead, the initial screening test of choice is the measurement of serum IGF-1. IGF-1 is synthesized by the liver in response to GH, has a longer half-life, and remains consistently elevated in patients with acromegaly, providing an accurate reflection of integrated GH secretion over time.

Step-by-Step Solution

Identify the clinical syndrome based on the patient's presentation.

The combination of acral enlargement (growing ring size, enlarged hands/feet), coarse facial features, macrognathia, diaphoresis, headaches, and new-onset hypertension is highly characteristic of acromegaly.

Recognizing the classic phenotype of excess growth hormone (GH) secretion is the first step in determining the diagnostic pathway.

Determine the optimal initial biochemical screening test for the suspected condition.

Measurement of serum insulin-like growth factor 1 (IGF-1) is the recommended initial screening test.

GH is secreted from the pituitary in a pulsatile fashion with a short half-life, making random GH levels unreliable. IGF-1 is produced by the liver in response to GH and provides a stable, integrated marker of GH secretion over time.

Sequence the subsequent diagnostic steps to follow the initial screen.

If IGF-1 is elevated, the next step is a confirmatory oral glucose suppression test. If GH fails to suppress, magnetic resonance imaging of the pituitary is then indicated.

Adhering to proper test sequencing avoids unnecessary imaging (which may reveal incidentalomas) and prevents the misinterpretation of fluctuating hormone levels.

Key Concept

The initial diagnostic test for suspected acromegaly is the measurement of serum insulin-like growth factor 1 (IGF-1) concentration, followed by an oral glucose suppression test if the IGF-1 level is elevated.

Question 4427Question →

A 19-year-old male college student is brought to the emergency department by his roommates because of confusion and a high fever. His roommates report that he complained of a severe headache and neck stiffness yesterday. Over the past few hours, he has become increasingly lethargic and developed a rapidly spreading purpuric rash on his lower extremities. He is oriented only to his name. His temperature is 39.8°C (103.6°F), blood pressure is 75/40 mmHg, heart rate is 138/min, respiratory rate is 26/min, and oxygen saturation is 94% on room air. The patient is moving all four extremities spontaneously.

Arrange the following management steps in the most appropriate sequential order for this patient.

Drag items to arrange them in the correct order

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Answer

The correct sequence is to first establish IV access, draw cultures, and start fluids, followed immediately by empiric antibiotics, then a head CT, and finally a lumbar puncture.

The patient presents with signs of septic shock and meningococcemia (purpuric rash, fever, neck stiffness, altered mental status). The first step in management is always initial stabilization: securing ABCs. He requires immediate IV access, blood cultures, and fluid resuscitation for his hypotension. Following this, empiric antibiotics must be administered without delay. Because he has altered mental status, he meets the criteria for requiring a head CT prior to a lumbar puncture to avoid cerebral herniation. Therefore, the CT scan is performed next, and the lumbar puncture follows once the CT is deemed safe.

Step-by-Step Solution

Assess the patient's hemodynamic status and establish circulation.

The patient is in shock (BP 75/40 mmHg) and requires immediate IV access, blood cultures, and crystalloid fluid resuscitation.

Airway and breathing are intact, so circulation is the primary initial stabilization priority.

Initiate definitive pharmacologic therapy.

Administer empiric intravenous ceftriaxone and vancomycin.

Early antibiotic administration is critical for survival in meningococcemia and bacterial meningitis; it must not be delayed for imaging.

Determine the safety of a lumbar puncture.

Identify that the patient has altered mental status (oriented only to name), necessitating a non-contrast head CT.

A head CT rules out mass effect to prevent cerebral herniation during the lumbar puncture.

Perform definitive diagnostic testing.

Perform a lumbar puncture to obtain cerebrospinal fluid.

Once the CT is cleared, CSF analysis is required to identify the specific pathogen and tailor antibiotic therapy.

Key Concept

In patients with suspected bacterial meningitis and shock, initial stabilization with fluids and empiric antibiotics takes precedence over diagnostic imaging and procedures. If the patient has altered mental status, a head CT must precede the lumbar puncture.

Question 4428Question →

For each of the following clinical vignettes featuring chronic gastrointestinal symptoms, select the most appropriate underlying etiology from the diagnostic options.

Click a left item, then click its matching right item

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Answer

Vignette 1 matches Microscopic colitis; Vignette 2 matches Crohn disease; Vignette 3 matches Whipple disease; Vignette 4 matches Bile acid malabsorption.

Formulating an accurate differential diagnosis for chronic diarrhea requires recognizing pattern clusters. Microscopic colitis presents with watery diarrhea and normal endoscopy in autoimmune patients. Crohn disease involves the terminal ileum, causing fat malabsorption and secondary oxalate stones. Whipple disease is a multisystem bacterial infection affecting the gut, joints, heart, and central nervous system. Bile acid malabsorption frequently occurs as a secretory diarrhea following cholecystectomy due to altered enterohepatic circulation.

Step-by-Step Solution

Evaluate the first vignette for characteristics of secretory diarrhea with a history of autoimmunity.

Identifies type 1 diabetes, nocturnal watery diarrhea, and a grossly normal mucosa with lymphocytic infiltrate.

These are the hallmark clinical and histological criteria for diagnosing microscopic colitis.

Analyze the second vignette for systemic complications of malabsorption and localized gastrointestinal disease.

Identifies steatorrhea, osteomalacia (bone pain), enteric hyperoxaluria (calcium oxalate stones), and perianal fistulas.

Fistulizing disease combined with terminal ileal malabsorption syndromes strongly confirms Crohn disease.

Assess the third vignette for multi-organ systemic involvement beyond the gastrointestinal tract.

Correlates chronic diarrhea with CNS (memory), joint (arthralgia), and cardiac (diastolic murmur) findings.

This specific multi-system symptom cluster points to systemic infection by Tropheryma whipplei.

Review the fourth vignette for a temporal relationship between surgery and symptom onset.

Links postprandial watery diarrhea to a prior cholecystectomy.

Loss of the gallbladder alters enterohepatic circulation, pointing to secondary bile acid malabsorption as the primary driver.

Key Concept

Differentiating etiologies of chronic diarrhea requires synthesizing gastrointestinal symptoms with specific extraintestinal manifestations, historical surgical risk factors, and histologic findings.

Question 4429Question →

Evaluation in the primary care clinic is requested for a $32$ -year-old woman who has experienced palpitations, diaphoresis, and an unintentional $4$ -kg ( $8.8$ -lb) weight loss over the past month. She reports no recent viral illnesses, neck pain, or changes in bowel habits. She has no significant past medical history and takes no prescription medications, though she recently started consuming an over-the-counter "metabolism-boosting" dietary supplement. Her blood pressure is $142/85$ mm Hg, and her pulse is $110$ /min. Physical examination reveals warm, moist skin and a fine bilateral tremor of the outstretched hands. There is no exophthalmos, and her thyroid gland is normal in size and non-tender on palpation.

Laboratory studies show the following:

Laboratory Test	Result	Reference Range
Thyroid-stimulating hormone (TSH)	$<0.01$ $\mu$ U/mL	$0.4-4.0$ $\mu$ U/mL
Free thyroxine (T4)	$3.8$ ng/dL	$0.8-1.8$ ng/dL
Total triiodothyronine (T3)	$240$ ng/dL	$80-200$ ng/dL
Thyroglobulin	$<1$ ng/mL	$3-40$ ng/mL
Thyroid-stimulating immunoglobulins	Negative	Negative

A $24$ -hour radioactive iodine uptake scan demonstrates an uptake of $1$ \% (Ref: $10$ \%- $30$ \%).

Based on the provided data, which of the following is the most likely diagnosis?

Exogenous thyroid hormone ingestion

Subacute granulomatous thyroiditis

Painless (silent) thyroiditis

Graves disease

Struma ovarii

Show answer & explanation

Answer: Exogenous thyroid hormone ingestion

Answer

Exogenous thyroid hormone ingestion

The correct diagnosis is exogenous thyroid hormone ingestion. The patient has clinical and biochemical thyrotoxicosis (low TSH, high T4/T3). The low radioactive iodine uptake (RAIU) indicates an absence of de novo hormone synthesis in the thyroid gland. The critical distinguishing factor is the nearly undetectable thyroglobulin level. Because thyroglobulin is produced exclusively by thyroid tissue, any endogenous cause of thyrotoxicosis (such as follicular destruction in thyroiditis or ectopic production in struma ovarii) would release thyroglobulin into the bloodstream. A low thyroglobulin level in the setting of thyrotoxicosis and a low RAIU is pathognomonic for an exogenous source of thyroid hormone, which in this case is likely hidden in the patient's 'metabolism-boosting' supplement.

Step-by-Step Solution

Interpret the basic thyroid panel (TSH, free T4, total T3).

The patient has a suppressed TSH and elevated T4/T3.

This confirms a state of primary thyrotoxicosis (hyperthyroidism), necessitating further workup to determine the etiology.

Evaluate the mechanism of thyrotoxicosis using the radioactive iodine uptake (RAIU) scan.

The RAIU is low (1%).

A low uptake indicates that the thyroid gland is suppressed and not actively synthesizing hormone de novo, effectively ruling out Graves disease and toxic nodular disease.

Differentiate the causes of low-uptake thyrotoxicosis by assessing the serum thyroglobulin level.

The thyroglobulin level is profoundly low (<1 ng/mL).

Thyroglobulin is co-secreted with thyroid hormones from endogenous thyroid tissue. Elevated levels suggest endogenous destruction (thyroiditis) or ectopic production (struma ovarii). Suppressed levels confirm the hormone is coming from an exogenous source, such as a supplement.

Key Concept

The serum thyroglobulin level is the critical laboratory test used to differentiate exogenous thyroid hormone ingestion (low thyroglobulin) from endogenous destructive thyroiditis or ectopic hormone production (high thyroglobulin) in a patient with thyrotoxicosis and a low radioactive iodine uptake.

Question 4430Question →

A primary care clinic is auditing health maintenance records to ensure adherence to 2026 evidence-based preventive care guidelines. Review the specific clinical scenarios below and pair each patient with the uniquely indicated preventive intervention.

Click a left item, then click its matching right item

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Answer

The correct pairings match the premenopausal woman to tamoxifen counseling, the immunosuppressed traveler to the inactivated typhoid vaccine, the hemodialysis patient to high-dose hepatitis B vaccination, the 38-year-old man with overweight to diabetes screening, and the pregnant patient to Tdap vaccination.

Each patient presentation represents a high-yield exception or specific modification to general screening and immunization guidelines. Premenopausal status dictates tamoxifen over raloxifene. Immunosuppression dictates inactivated over live vaccines. Hemodialysis requires specialized high-dose vaccination protocols. Overweight status in adults over 35 triggers diabetes screening, and pregnancy triggers routine Tdap regardless of prior interval.

Step-by-Step Solution

Evaluate the 48-year-old woman's breast cancer risk and menopausal status.

Her 5-year risk is elevated (3.8%) due to atypical ductal hyperplasia, and she is premenopausal.

To determine eligibility and the correct choice of chemoprevention (tamoxifen vs. raloxifene).

Assess the travel medicine needs of the 65-year-old woman on etanercept.

She requires typhoid prophylaxis but cannot receive live-attenuated vaccines due to TNF inhibitor therapy.

Immunocompromise creates strict contraindications for specific vaccine formulations, guiding the choice toward the inactivated vaccine.

Identify the vaccination requirements for the 52-year-old hemodialysis patient.

He requires hepatitis B vaccination using a high-dose or adjuvanted formulation.

Uremia impairs immune response, necessitating altered dosing strategies to achieve appropriate seroprotection.

Apply current USPSTF metabolic screening guidelines to the 38-year-old man.

With a BMI of 28 kg/m², he requires screening for abnormal blood glucose.

Guidelines mandate diabetes screening starting at age 35 for all adults with overweight or obesity.

Determine the prenatal vaccination protocol for the 28-week pregnant patient.

She must receive the Tdap vaccine immediately, regardless of her recent Td booster.

To maximize maternal antibody production and transplacental transfer for infant pertussis protection.

Key Concept

Application of nuanced preventive care guidelines based on specific patient demographics, immune status, and comorbidities.

Question 4431Question →

A 68-year-old man comes to the clinic due to a 6-week history of painful swelling in his wrists and ankles. The pain is severe, deep, aching, and exacerbated by weight-bearing. He also reports a 3-month history of a persistent dry cough and an unintentional 4-kg (8.8-lb) weight loss. He has a 40-pack-year smoking history but quit 5 years ago. His temperature is 37.2°C (99.0°F), blood pressure is 138/86 mmHg, heart rate is 88/min, and respiratory rate is 16/min. Physical examination reveals bulbous enlargement of the fingertips with increased convexity of the nail beds. There is palpable tenderness and warmth over the distal tibia, fibula, radius, and ulna bilaterally. Lung auscultation reveals decreased breath sounds and dullness to percussion in the right upper lobe. Complete blood count and basic metabolic panel are within normal limits. Plain radiographs of the lower extremities show symmetric, bilateral periosteal new bone formation along the distal diaphyses of the tibia and fibula. Which of the following is the most likely underlying diagnosis?

Non-small cell lung cancer

Rheumatoid arthritis

Idiopathic pulmonary fibrosis

Granulomatosis with polyangiitis

Bronchiectasis

Show answer & explanation

Answer: Non-small cell lung cancer

Answer

The correct diagnosis is non-small cell lung cancer.

The correct answer is non-small cell lung cancer. This patient's clinical presentation—digital clubbing, sudden-onset painful arthropathy, and radiographic evidence of periosteal new bone formation (periostitis)—constitutes the classic triad of hypertrophic pulmonary osteoarthropathy (HPOA). HPOA is a paraneoplastic syndrome that is strongly associated with intrathoracic malignancies, most notably non-small cell lung cancer (especially adenocarcinoma). The presence of a prominent smoking history, constitutional symptoms (weight loss), and focal right upper lobe physical exam findings (decreased breath sounds and dullness to percussion) further points toward a primary pulmonary malignancy as the underlying driver of his systemic symptoms.

Step-by-Step Solution

Synthesize the osteoarticular physical exam and radiographic findings.

The patient has digital clubbing (bulbous fingertips), arthritis/arthralgias (warmth/tenderness in wrists and ankles), and radiographic evidence of periostitis (periosteal new bone formation).

Recognizing this specific combination of symptoms as the triad of hypertrophic pulmonary osteoarthropathy (HPOA) narrows the differential diagnosis to thoracic pathologies.

Correlate the systemic paraneoplastic syndrome with the pulmonary findings and risk factors.

The patient has a 40-pack-year smoking history, weight loss, and focal right upper lobe findings (decreased breath sounds, dullness to percussion) suggestive of a pulmonary mass.

HPOA is most strongly associated with underlying intrathoracic malignancies, specifically primary lung cancer, which fits perfectly with the mass-like exam findings and smoking history.

Select the most appropriate primary diagnosis from the available options.

Non-small cell lung cancer (NSCLC), particularly adenocarcinoma, is the most common cause of HPOA.

Other options may explain isolated symptoms (like clubbing in bronchiectasis or joint pain in rheumatoid arthritis) but fail to explain the entire clinical and radiographic picture.

Key Concept

Hypertrophic pulmonary osteoarthropathy (HPOA) presents with digital clubbing, arthropathy, and periostitis, and is a paraneoplastic syndrome highly suggestive of an underlying non-small cell lung cancer.

Question 4432Question →

A 42-year-old construction worker is brought to the trauma resuscitation bay following a 20-foot fall from a scaffold. On arrival, he is pale and lethargic but moans in response to painful stimuli. His airway is patent, and breath sounds are vesicular and equal bilaterally.

Vital signs are:
Temperature: 36.4°C (97.5°F)
Blood pressure: 72/40 mmHg
Heart rate: 135 /min
Respiratory rate: 24 /min
Oxygen saturation: 97% on high-flow oxygen.

A primary survey reveals a mechanically unstable pelvis that demonstrates mobility on gentle anterior-posterior compression. There are severe abrasions over the lower abdomen and flanks, but no obvious sources of external hemorrhage are identified. Two large-bore peripheral intravenous lines are immediately established.

Which of the following are the most appropriate immediate next steps in management? (Select two)

Select all that apply

Application of a pelvic circumferential compression device

Administration of uncrossmatched blood products

Computed tomography angiography of the pelvis

Urgent magnetic resonance imaging of the lumbosacral spine

Immediate transfer to the general orthopedic ward

Show answer & explanation

Answer: Application of a pelvic circumferential compression device; Administration of uncrossmatched blood products

Answer

The most appropriate immediate next steps are the application of a pelvic circumferential compression device and the administration of uncrossmatched blood products.

The correct sequence for managing this hemodynamically unstable patient with a suspected pelvic fracture relies on immediate life-saving interventions. The application of a pelvic circumferential compression device reduces the intrapelvic volume, which helps to tamponade venous bleeding and stabilize the fractured bone ends. Concurrently, because the patient is in Class IV hemorrhagic shock (hypotension, severe tachycardia, altered mental status), the immediate administration of uncrossmatched blood products is essential to rapidly restore intravascular volume and oxygen-carrying capacity. These steps must occur simultaneously in the trauma bay before any advanced diagnostic imaging or definitive disposition is considered.

Step-by-Step Solution

Assess the patient's hemodynamic status based on vital signs and physical examination.

The patient has a blood pressure of 72/40 mmHg, a heart rate of 135 /min, and lethargy, indicating severe (Class IV) hypovolemic shock.

Recognizing the severity of shock dictates the urgency and type of fluid resuscitation required.

Identify the likely source of hemorrhage.

The primary survey reveals a mechanically unstable pelvis without obvious external bleeding, suggesting massive retroperitoneal hemorrhage from a pelvic ring disruption.

Identifying the hemorrhage source directs specific mechanical stabilization measures.

Select the appropriate stabilization interventions.

A pelvic binder must be applied to reduce pelvic volume and tamponade bleeding, while uncrossmatched blood products must be administered to treat the hemorrhagic shock.

In unstable trauma patients, immediate mechanical stabilization and volume replacement with blood take absolute precedence over advanced diagnostic imaging.

Key Concept

In patients with severe hemorrhagic shock due to an unstable pelvic fracture, initial management must focus on immediate mechanical stabilization (pelvic binder) and balanced hemostatic resuscitation (uncrossmatched blood products) before transporting the patient for advanced imaging.

Estimated Time:1m 30s

Question 4433Question →

Emergency medical responders bring a 55-year-old woman to the emergency department due to bilateral lower extremity weakness that began 48 hours ago. She reports a four-week history of relentless, deep mid-back pain that frequently awakens her from sleep and is refractory to over-the-counter analgesics. Her past medical history is significant for estrogen-receptor-positive breast cancer, for which she completed adjuvant endocrine therapy one year ago. On physical examination, her temperature is 37.2°C (99.0°F), blood pressure is 135/85 mm Hg, and pulse is 92/min. There is focal tenderness to percussion over the T9 and T10 spinous processes. Neurological evaluation reveals 3/5 motor strength in the bilateral hip flexors, knee extensors, and ankle dorsiflexors. Deep tendon reflexes are 3+ at the patellae and Achilles bilaterally. Upgoing plantar reflexes (positive Babinski sign) are noted bilaterally. Pinprick sensation is markedly diminished below the level of the umbilicus. Rectal examination demonstrates decreased anal sphincter tone.

Based on the clinical presentation, arrange the following differential diagnoses from most likely (top) to least likely (bottom).

Drag items to arrange them in the correct order

Show answer & explanation

Answer

The correct order of differential diagnoses from most to least likely is: Malignant epidural spinal cord compression, Spinal epidural abscess, Transverse myelitis, and Lumbar disc herniation.

The clinical picture of progressive thoracic back pain that awakens the patient from sleep, coupled with a history of breast cancer and new-onset upper motor neuron signs (hyperreflexia, positive Babinski, T10 sensory level), is the textbook presentation of malignant spinal cord compression. Spinal epidural abscess follows as the second most likely because it is another compressive etiology that can produce identical neurological deficits, though it is less probable here due to the absence of infectious signs or risk factors. Transverse myelitis is third; while it causes myelopathy, the 4-week history of localized skeletal pain strongly favors an extrinsic compressive mass over intrinsic cord inflammation. Lumbar disc herniation is the least likely as it is anatomically incorrect for a T10 sensory level and presents with lower motor neuron signs, not upper motor neuron signs.

Step-by-Step Solution

Identify the 'red flag' historical features in the patient's presentation.

The patient has localized mid-back pain that is worse at night and a prior history of breast cancer.

These findings are highly suspicious for a neoplastic process, particularly spinal metastasis.

Localize the neurological lesion based on physical examination findings.

Bilateral hyperreflexia, upgoing plantar reflexes (positive Babinski), and a distinct sensory level at the umbilicus (T10 dermatome).

These are classic upper motor neuron (UMN) signs indicating a central nervous system lesion in the thoracic spinal cord, ruling out peripheral or lumbar nerve root causes.

Prioritize the etiologies based on time course and anatomical compatibility.

An epidural mass effect (tumor or abscess) perfectly explains the prolonged local pain followed by acute cord compression. Malignancy is prioritized over abscess due to the lack of infectious risk factors. Transverse myelitis lacks the long bony pain prodrome.

This logical progression establishes the diagnostic hierarchy from highest pre-test probability to lowest.

Key Concept

Prioritization of spinal cord compression etiologies using neurological localization and historical risk factors.

Question 4434Question →

A 34-year-old man is brought to the emergency department by emergency medical services after being rescued from a closed-space house fire. He was found trapped in a smoke-filled bedroom. On arrival, he is awake but agitated. Physical examination reveals partial- and full-thickness burns over his anterior chest and bilateral upper extremities. He has singed nasal vibrissae, carbonaceous sputum in the oropharynx, and a noticeably hoarse voice. Vital signs are temperature 37.1°C (98.8°F), blood pressure 110/70 mmHg, pulse 115/min, and respirations 28/min. Pulse oximetry shows an oxygen saturation of 94% on a 15 L/min non-rebreather face mask. Which of the following is the most appropriate immediate next step in the stabilization of this patient?

Endotracheal intubation

Calculation of total body surface area burned and initiation of lactated Ringer solution

Arterial blood gas analysis with co-oximetry

Portable chest radiography

Diagnostic flexible bronchoscopy

Show answer & explanation

Answer: Endotracheal intubation

Answer

The correct answer is endotracheal intubation.

The correct answer is endotracheal intubation. In any trauma or burn patient, the primary survey rigorously follows the ABCs (Airway, Breathing, Circulation). This patient presents with a history of closed-space fire exposure and physical findings highly indicative of thermal inhalation injury, including singed nasal vibrissae, carbonaceous sputum, and a newly hoarse voice. Thermal injury to the upper airway can lead to rapidly progressive, severe edema, resulting in complete airway obstruction. Because the airway can swell shut in a matter of minutes to hours, early and prophylactic endotracheal intubation is the most critical and immediate step. It secures the airway before it becomes anatomically impossible to intubate. Other diagnostic and therapeutic interventions, while important, must follow the establishment of a definitive airway.

Step-by-Step Solution

Identify the primary life threat based on the clinical presentation.

The patient's hoarse voice, singed nasal vibrissae, and carbonaceous sputum after a closed-space fire strongly suggest thermal inhalation injury to the upper airway.

Thermal injury causes rapid and progressive tissue edema that can quickly lead to complete upper airway obstruction.

Apply the initial trauma and burn resuscitation algorithm.

The ABCs (Airway, Breathing, Circulation) mandate that airway management takes ultimate precedence.

Without a patent airway, all other resuscitative and diagnostic efforts will fail to prevent hypoxemia and death.

Determine the most appropriate intervention for the identified threat.

Early endotracheal intubation is selected.

Prophylactic intubation secures the airway definitively before progressive swelling makes the procedure anatomically difficult or impossible.

Key Concept

In patients with clinical signs of thermal inhalation injury (e.g., singed facial hair, soot in the oropharynx, hoarseness), early and prophylactic endotracheal intubation is the immediate priority to prevent complete airway obstruction from progressive edema.

Estimated Time:1m 15s

Question 4435Question →

Review the following viral hepatitis serologic testing panels obtained during routine outpatient screening. Connect each specific laboratory profile to its most accurate clinical interpretation.

Click a left item, then click its matching right item

Show answer & explanation

Answer

The correct mapping aligns acute infection with HBsAg/IgM anti-HBc, chronic infection with HBsAg/IgG anti-HBc, past natural infection immunity with anti-HBs/IgG anti-HBc, and vaccine immunity with isolated anti-HBs.

Matching viral serology requires a systematic approach. HBsAg determines active disease versus no active disease. Anti-HBc determines if the patient has ever encountered the actual virus (IgM for acute, IgG for past/chronic). Anti-HBs determines immunity. Together, these markers create distinct, non-overlapping profiles for acute infection, chronic infection, natural immunity, and vaccine-induced immunity.

Step-by-Step Solution

Analyze the HBsAg (surface antigen) status.

Positive HBsAg indicates current active infection (either acute or chronic). Negative HBsAg indicates the absence of active infection (either resolved or uninfected/vaccinated).

HBsAg is the primary marker of active viral replication and presence in the bloodstream.

Evaluate the anti-HBc (core antibody) testing.

IgM anti-HBc points to a recent, acute infection. IgG anti-HBc points to a past exposure (which may be chronic if HBsAg remains positive, or resolved if HBsAg is negative).

The core antigen is not present in the vaccine, so anti-HBc is only produced during a true natural viral infection. The IgM-to-IgG transition marks the passage of time.

Check the anti-HBs (surface antibody) status.

Positive anti-HBs indicates immunity. When combined with negative anti-HBc, it proves vaccination. When combined with positive anti-HBc IgG, it proves recovery from natural infection.

Anti-HBs is the neutralizing antibody that provides long-term immunity.

Key Concept

Interpretation of Hepatitis B Serologic Markers

Question 4436Question →

A 28-year-old woman, G2P1, at 26 weeks gestation, presents to the emergency department with acute-onset right-sided pleuritic chest pain and shortness of breath. She has no significant past medical history. Vital signs show a heart rate of 115/min, respiratory rate of 24/min, and oxygen saturation of 94% on room air. Physical examination is unremarkable with clear lungs and normal heart sounds. The patient's presentation is highly suspicious for a pulmonary embolism (PE).

Arrange the following diagnostic modalities in the most appropriate sequential order for the evaluation of this patient, from the initial test to the final definitive imaging study if preceding tests are nondiagnostic.

Drag items to arrange them in the correct order

Show answer & explanation

Answer

The correct sequence is: Chest radiography -> Bilateral lower extremity compression ultrasonography -> Ventilation-perfusion (V/Q) lung scintigraphy -> Computed tomography pulmonary angiography (CTPA).

The established algorithm for evaluating suspected pulmonary embolism in pregnancy prioritizes minimizing radiation exposure to both the fetus and maternal breast tissue. The sequence begins with a chest radiograph to rule out alternative diagnoses. If normal, a radiation-free lower extremity ultrasound is performed to check for DVT, which would independently mandate anticoagulation. If the ultrasound is negative, a V/Q scan is preferred due to lower maternal breast radiation. CTPA is reserved strictly for cases where the V/Q scan is non-diagnostic or if the initial CXR was abnormal.

Step-by-Step Solution

Evaluate the clinical presentation and rule out alternative diagnoses.

A chest radiograph (CXR) is the initial step to exclude conditions like pneumonia and to verify that the lungs are clear for a subsequent V/Q scan.

V/Q scanning requires a normal CXR to be accurately interpreted.

Select the most appropriate initial radiation-free imaging modality if the CXR is normal.

Bilateral lower extremity compression ultrasonography is performed.

It involves zero ionizing radiation. If a deep vein thrombosis is found, the patient can be treated immediately, avoiding fetal or maternal radiation exposure from further chest imaging.

Determine the next cross-sectional imaging step if ultrasound is negative.

A ventilation-perfusion (V/Q) scan is ordered.

In the setting of a normal CXR, a V/Q scan is preferred as the initial definitive imaging for PE in pregnancy due to a lower radiation dose to maternal breast tissue compared to CTPA.

Identify the final definitive test if preceding modalities are nondiagnostic.

Computed tomography pulmonary angiography (CTPA) is performed.

CTPA is utilized as a definitive diagnostic test when the V/Q scan is indeterminate or if the initial CXR was abnormal.

Key Concept

In pregnant patients with suspected pulmonary embolism, diagnostic sequencing aims to minimize fetal and maternal breast radiation by prioritizing chest radiography and lower extremity ultrasonography before proceeding to V/Q scanning or CT pulmonary angiography.

Question 4437Question →

A 60-year-old woman presents to the clinic for a routine health maintenance examination. She has a history of type 2 diabetes mellitus and early-stage right breast cancer, which was treated with lumpectomy and local radiation therapy at age 52. She declined adjuvant endocrine therapy. Her diabetes is well-controlled with metformin. She has a 35-pack-year smoking history but successfully quit 8 years ago.

Her preventive care history is as follows:
- Colonoscopy at age 54 was completely normal.
- Screening mammogram 2 months ago showed no evidence of malignancy.
- Hepatitis C antibody test at age 55 was negative.
- Received a Tdap booster 4 years ago.
- Completed the sequence of PCV15 followed by PPSV23 one year ago.
- She has never received a zoster vaccine.

Which of the following preventive interventions are indicated for this patient at this visit? (Select all that apply)

Select all that apply

Dual-energy x-ray absorptiometry scan

Low-dose chest computed tomography

Recombinant zoster vaccine

Screening colonoscopy

20-valent pneumococcal conjugate vaccine

Show answer & explanation

Answer: Low-dose chest computed tomography; Recombinant zoster vaccine

Answer

The indicated preventive interventions are low-dose chest computed tomography (LDCT) and the recombinant zoster vaccine.

Low-dose chest computed tomography (LDCT) is indicated because the USPSTF recommends annual screening for adults aged 50 to 80 years with a 20 pack-year smoking history who currently smoke or quit within the past 15 years. This patient meets all criteria. The recombinant zoster vaccine is indicated because the ACIP recommends a 2-dose series for all adults aged 50 years and older to prevent herpes zoster. Since she has never received it, the first dose should be administered.

Step-by-Step Solution

Evaluate the patient's lung cancer risk based on her age and smoking history.

The patient is 60 years old, has a 35-pack-year smoking history, and quit 8 years ago.

To determine if she meets the current USPSTF criteria for annual LDCT screening.

Assess the patient's vaccination status against ACIP adult schedules.

The patient is 60 (eligible for the zoster vaccine, which starts at age 50) and has already completed her indicated pneumococcal series.

To identify any missing age-based or risk-based immunizations.

Review the intervals for previously performed screening tests.

The patient had a normal colonoscopy 6 years ago (next due in 4 years) and is 60 years old without elevated fracture risk (DEXA due at 65).

To prevent premature or redundant testing.

Key Concept

Evidence-based preventive care involves applying age-, gender-, and risk-specific guidelines (e.g., USPSTF, ACIP) to determine the appropriate timing and intervals for cancer screenings and immunizations.

Question 4438Question →

Accompanied by her husband, a 28-year-old woman arrives at the emergency department presenting with progressive lethargy, confusion, and subjective fever over the past two days. Her husband mentions she had been complaining of an intense headache and recently developed a pinpoint red rash on her calves. She has a known history of systemic lupus erythematosus (SLE) diagnosed three years ago, managed with hydroxychloroquine and a low-dose oral corticosteroid.

Her temperature is $38.1^\circ\text{C}$ ( $100.6^\circ\text{F}$ ), blood pressure is $142/88 \text{ mmHg}$ , pulse is $105/\text{min}$ , and respirations are $18/\text{min}$ . Physical examination reveals scattered petechiae on the bilateral lower extremities. Neurological examination shows she is oriented to person and place only, but there are no focal motor or sensory deficits.

Laboratory results are as follows:

Laboratory Test	Result	Reference Range
Hemoglobin	$7.8 \text{ g/dL}$	$12.0-15.5 \text{ g/dL}$
Platelets	$24,000/\text{mm}^3$	$150,000-400,000/\text{mm}^3$
Leukocytes	$6,500/\text{mm}^3$	$4,500-11,000/\text{mm}^3$
Creatinine	$1.6 \text{ mg/dL}$	$0.6-1.1 \text{ mg/dL}$
Total bilirubin	$3.2 \text{ mg/dL}$	$0.1-1.2 \text{ mg/dL}$
Indirect bilirubin	$2.7 \text{ mg/dL}$	$0.1-0.8 \text{ mg/dL}$
Lactate dehydrogenase (LDH)	$1,150 \text{ U/L}$	$140-280 \text{ U/L}$
Prothrombin time (PT)	$12 \text{ seconds}$	$11-15 \text{ seconds}$
Activated partial thromboplastin time (aPTT)	$32 \text{ seconds}$	$25-40 \text{ seconds}$
Direct antiglobulin test (DAT)	Negative	Negative

The peripheral blood smear reveals prominent schistocytes and severely decreased platelets.

Based on the clinical evaluation and laboratory data, which of the following is the most likely diagnosis?

Thrombotic thrombocytopenic purpura

Systemic lupus erythematosus disease flare

Disseminated intravascular coagulation

Evans syndrome

Meningococcal meningitis

Show answer & explanation

Answer: Thrombotic thrombocytopenic purpura

Answer

The most likely diagnosis is thrombotic thrombocytopenic purpura.

The correct diagnosis is thrombotic thrombocytopenic purpura (TTP). TTP is a life-threatening thrombotic microangiopathy typically caused by a severe deficiency of the ADAMTS13 protease, which leads to the formation of large von Willebrand factor multimers that shear red blood cells and consume platelets. It is classically defined by a pentad of clinical findings: microangiopathic hemolytic anemia (MAHA), thrombocytopenia, acute kidney injury, neurological abnormalities, and fever. This patient exhibits all five features. The peripheral smear showing schistocytes, combined with elevated LDH and indirect bilirubin, confirms mechanical hemolysis (MAHA). Crucially, the normal coagulation studies (PT and aPTT) differentiate TTP from consumptive coagulopathies like disseminated intravascular coagulation (DIC). Acquired TTP is often associated with autoantibodies, and patients with underlying autoimmune diseases, such as systemic lupus erythematosus (SLE), are at a higher risk of developing it.

Step-by-Step Solution

Identify the patient's primary clinical syndrome from the physical and historical findings.

The patient has altered mental status, fever, and petechiae (indicative of thrombocytopenia).

Establishing the clinical pillars helps guide the interpretation of laboratory results.

Analyze the laboratory data and peripheral smear to characterize the cytopenias.

Labs show severe thrombocytopenia and anemia. Elevated LDH, indirect hyperbilirubinemia, and schistocytes confirm a microangiopathic hemolytic anemia (MAHA).

Differentiating mechanical intravascular hemolysis (schistocytes, negative DAT) from immune extravascular hemolysis (spherocytes, positive DAT) is critical for diagnosis.

Assess the coagulation cascade markers (PT and aPTT).

Both PT and aPTT are within normal limits.

Normal coagulation times rule out consumptive coagulopathies like DIC, narrowing the differential to primary thrombotic microangiopathies.

Synthesize the findings to formulate the final diagnosis.

The classic pentad of MAHA, thrombocytopenia, fever, renal impairment, and neurological symptoms in the setting of normal coagulation studies points directly to TTP.

Patients with preexisting autoimmune conditions (like SLE) have a known increased risk of developing acquired TTP (due to autoantibodies against ADAMTS13).

Key Concept

Thrombotic thrombocytopenic purpura (TTP) is a life-threatening thrombotic microangiopathy characterized by microangiopathic hemolytic anemia, thrombocytopenia, neurological symptoms, renal impairment, and fever, all in the setting of normal coagulation studies (PT/aPTT).

Question 4439Question →

Emergency medical services bring a primigravid patient at $34$ weeks gestation to the obstetric triage unit after she developed acute, severe right upper quadrant abdominal pain and recurrent vomiting. Her blood pressure is $162/98$ mm Hg, and her pulse is $94$ /min. Physical examination demonstrates marked tenderness just below the right costal margin. Laboratory studies reveal the following:

Test	Result	Reference Range
Hemoglobin	$8.9$ g/dL	$11.0-14.0$ g/dL
Platelets	$52,000$ /mm³	$150,000-400,000$ /mm³
Aspartate aminotransferase (AST)	$285$ U/L	$10-40$ U/L
Alanine aminotransferase (ALT)	$290$ U/L	$10-40$ U/L
Total bilirubin	$2.4$ mg/dL	$0.2-1.2$ mg/dL
Prothrombin time (PT)	$12.5$ sec	$11-15$ sec
Activated partial thromboplastin time (aPTT)	$32$ sec	$25-40$ sec
Fibrinogen	$420$ mg/dL	$300-600$ mg/dL (in pregnancy)

A peripheral blood smear demonstrates numerous schistocytes.

Based on the interpretation of these laboratory results, which of the following is the most likely diagnosis?

Acute fatty liver of pregnancy

Disseminated intravascular coagulation

HELLP syndrome

Immune thrombocytopenia

Thrombotic thrombocytopenic purpura

Show answer & explanation

Answer: HELLP syndrome

Answer

HELLP syndrome

The correct answer accurately identifies HELLP syndrome, which is defined by the triad of Hemolysis (evidenced by anemia, schistocytes, and elevated bilirubin), Elevated Liver enzymes (transaminitis), and Low Platelets. A critical distinguishing factor in interpreting laboratory results for HELLP is that, unlike disseminated intravascular coagulation (DIC) or acute fatty liver of pregnancy (AFLP), the coagulation studies (PT, aPTT, and fibrinogen) remain completely normal until catastrophic complications (such as liver rupture or secondary DIC) occur.

Step-by-Step Solution

Identify the signs of microangiopathic hemolytic anemia (MAHA) and liver involvement.

The patient has anemia, schistocytes, and elevated indirect bilirubin (hemolysis), along with elevated AST/ALT and low platelets.

These findings establish the classic triad of Hemolysis, Elevated Liver enzymes, and Low Platelets.

Evaluate the coagulation cascade laboratory results (PT, aPTT, fibrinogen).

The PT, aPTT, and fibrinogen levels are all within normal reference ranges.

Normal coagulation studies are critical to exclude consumptive coagulopathies and severe synthetic liver failure.

Synthesize the laboratory data with the clinical context to determine the diagnosis.

A third-trimester pregnant patient with MAHA, transaminitis, thrombocytopenia, and normal coagulation studies most likely has HELLP syndrome.

This specific laboratory profile successfully differentiates HELLP from acute fatty liver of pregnancy (AFLP) and disseminated intravascular coagulation (DIC).

Key Concept

Distinguishing microangiopathic hemolytic anemias and liver pathologies in pregnancy primarily relies on interpreting the coagulation profile (PT, aPTT, fibrinogen) alongside basic metabolic and hematologic markers.

Estimated Time:1m 30s

Question 4440Question →

A neurology consultation service evaluates multiple patients presenting with parkinsonian features. For each clinical presentation described below, formulate the most appropriate differential diagnosis by matching the patient vignette to the most likely underlying condition.

Click a left item, then click its matching right item

Show answer & explanation

Answer

The presentations map to their respective syndromes based on core distinguishing features: vertical gaze palsy indicates Progressive supranuclear palsy; severe autonomic dysfunction indicates Multiple system atrophy; prominent visual hallucinations with cognitive fluctuations indicate Dementia with Lewy bodies; and isolated asymmetric resting tremor with REM sleep behavior disorder indicates Idiopathic Parkinson disease.

Formulating an accurate differential diagnosis for parkinsonian syndromes requires identifying specific historical and examination findings. Progressive supranuclear palsy presents with early postural instability and supranuclear vertical gaze palsy. Multiple system atrophy presents with parkinsonism and early, severe autonomic failure. Dementia with Lewy bodies is distinguished by early cognitive fluctuations and visual hallucinations. Idiopathic Parkinson disease classically presents with an asymmetric resting tremor and is frequently preceded by non-motor symptoms like REM sleep behavior disorder.

Step-by-Step Solution

Analyze the first presentation focusing on backward falls and impaired vertical gaze.

The clinical findings strongly suggest Progressive supranuclear palsy.

Impairment of vertical eye movements and early postural instability are the defining 'red flags' for this condition.

Evaluate the second presentation highlighting profound autonomic failure alongside parkinsonism.

The clinical picture aligns with Multiple system atrophy.

Parkinsonism combined with severe dysautonomia (historically termed Shy-Drager syndrome) is the classic presentation.

Review the third presentation featuring fluctuating cognition and visual hallucinations.

These are the core diagnostic criteria for Dementia with Lewy bodies.

Early cognitive changes with detailed visual hallucinations differentiate this from the later-stage dementia seen in Parkinson disease.

Examine the fourth presentation with unilateral resting tremor, anosmia, and dream enactment.

This is characteristic of Idiopathic Parkinson disease.

It represents the classic presentation with unilateral onset, typical resting tremor, and recognized prodromal features.

Key Concept

Differentiating atypical parkinsonian syndromes (Parkinson-plus syndromes) from idiopathic Parkinson disease requires identifying unique clinical features such as gaze palsies, early autonomic failure, and early hallucinations.

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