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Question 1601Question →

A 38-year-old patient is admitted to the diagnostic evaluation unit for recurrent episodes of diaphoresis, palpitations, and confusion that resolve rapidly with carbohydrate intake. A supervised 72-hour fasting test is initiated, and comprehensive laboratory studies are drawn when the patient develops symptomatic hypoglycemia (capillary blood glucose 42 mg/dL). Match each distinct laboratory profile below with its most likely underlying pathophysiologic mechanism.

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Items

Serum insulin elevated, C-peptide elevated, proinsulin elevated, negative oral secretagogue screen
Serum insulin elevated, C-peptide suppressed, proinsulin suppressed, negative oral secretagogue screen
Serum insulin elevated, C-peptide elevated, proinsulin normal, positive oral secretagogue screen
Serum insulin suppressed, C-peptide suppressed, elevated IGF-II, low beta-hydroxybutyrate

Matches

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Answer

Profile L1 matches autonomous exocytosis (insulinoma). Profile L2 matches direct hormone administration (exogenous insulin). Profile L3 matches K-ATP channel closure (sulfonylurea). Profile L4 matches paraneoplastic receptor activation (non-islet cell tumor hypoglycemia).
Each laboratory profile uniquely maps to a pathophysiologic mechanism of hypoglycemia. Elevated insulin with high C-peptide and a negative drug screen points to an insulinoma (autonomous neuroendocrine secretion). High insulin with low C-peptide indicates exogenous insulin injection, as commercial preparations lack the cleavage byproduct. High insulin and C-peptide with a positive drug screen confirms sulfonylurea use, which pharmacologically closes K-ATP channels. Low insulin and C-peptide with high IGF-II indicates a paraneoplastic syndrome where the tumor secretes a peptide that activates peripheral insulin receptors.

Step-by-Step Solution

1
Analyze the relationship between serum insulin and C-peptide to differentiate endogenous from exogenous hyperinsulinemia.
Elevated insulin with suppressed C-peptide identifies exogenous administration, while concurrent elevation of both points to an endogenous source.
Endogenous insulin is secreted in a 1:1 equimolar ratio with C-peptide, whereas pharmaceutical insulin preparations do not contain C-peptide.
2
Evaluate the oral secretagogue screen in profiles with endogenous hyperinsulinemia.
A positive screen identifies pharmacologic stimulation of beta cells, whereas a negative screen points to autonomous tumor secretion.
Sulfonylureas and meglitinides artificially stimulate endogenous insulin release by closing K-ATP channels, mimicking an insulinoma.
3
Identify non-insulin-mediated mechanisms in profiles with suppressed insulin and C-peptide.
Hypoglycemia with suppressed beta-cell function and elevated IGF-II indicates a paraneoplastic syndrome.
Tumor-secreted IGF-II binds to insulin receptors, driving glucose into tissues while appropriately suppressing endogenous pancreatic beta-cell activity via negative feedback.

Key Concept

Pathophysiologic mechanisms and diagnostic laboratory profiles of fasting hypoglycemia
Question 1602Question →

A 45-year-old woman is diagnosed with Zollinger-Ellison syndrome after presenting with chronic diarrhea and recurrent, medically refractory peptic ulcers. Her fasting serum gastrin level is 2,400 pg/mL (normal: < 100 pg/mL) while off proton pump inhibitors, and her gastric fluid pH is 1.5. A secretin stimulation test demonstrates a paradoxical rise in serum gastrin of 350 pg/mL. An initial multiphase contrast-enhanced computed tomography (CT) scan of the abdomen and pelvis performed at a community hospital reveals no discrete pancreatic or hepatic masses. She is referred to a tertiary care center for surgical evaluation.

Arrange the following advanced imaging and localization modalities in the most appropriate chronological sequence to pinpoint the location of the primary neuroendocrine tumor.

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Answer

The correct diagnostic imaging sequence is to first perform a Gallium-68 DOTATATE PET/CT, followed by Endoscopic Ultrasonography (EUS) if further anatomic detail is needed or the PET/CT is negative, and finally utilizing Selective Arterial Secretin Injection (SASI) only if the tumor remains occult on all prior imaging.
The stepwise evaluation of a biochemically confirmed gastrinoma (Zollinger-Ellison syndrome) with an initially negative standard CT scan prioritizes the most sensitive, least invasive modalities first. Gallium-68 DOTATATE PET/CT is a functional scan that binds to somatostatin receptors (highly expressed on gastrinomas) and provides excellent whole-body localization for both the primary tumor and potential metastases, making it the ideal first step. If the PET/CT is negative, Endoscopic Ultrasonography (EUS) is the next logical step, as it provides extremely high-resolution imaging of the 'gastrinoma triangle' (the duodenum and pancreatic head) and can detect tumors smaller than 5 millimeters. Finally, if both PET/CT and EUS fail to localize the tumor, Selective Arterial Secretin Injection (SASI) with hepatic venous sampling is performed. This highly invasive angiographic procedure localizes the tumor by mapping the vascular territory that secretes gastrin in response to secretin stimulation.

Step-by-Step Solution

1
Order whole-body functional receptor imaging
Perform Gallium-68 DOTATATE PET/CT
To conduct a highly sensitive, non-invasive whole-body assessment for somatostatin receptor-expressing primary tumors and distant metastases, which is the standard next step when conventional CT is unrevealing.
2
Order high-resolution regional luminal imaging
Perform Endoscopic Ultrasonography (EUS)
To evaluate the gastrinoma triangle with high sensitivity for microadenomas (less than 1 cm) in the duodenal wall or pancreatic head, utilized if functional imaging is negative or equivocal.
3
Order invasive regional venous sampling
Perform Selective Arterial Secretin Injection (SASI)
To serve as a functional mapping test of last resort to locate the regional blood supply of a biochemically proven but anatomically occult gastrinoma prior to exploratory laparotomy.

Key Concept

Sequencing of diagnostic imaging for localization of occult neuroendocrine tumors (gastrinomas) in Zollinger-Ellison Syndrome
Estimated Time:1m 30s
Question 1603Question →

Match the following thyroid laboratory profiles to their most likely diagnostic etiology.

Reference Ranges:
TSH: 0.4−4.00.4-4.0 μ\mu U/mL
Free T4: 0.9−2.40.9-2.4 ng/dL
Total T3: 80−20080-200 ng/dL
24-hour Radioactive Iodine Uptake (RAIU): 10−30%10-30\%

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Items

Profile 1: TSH 0.010.01 μ\mu U/mL, Free T4 2.92.9 ng/dL, 24-hour RAIU 2%2\%
Profile 2: TSH 12.512.5 μ\mu U/mL, Free T4 0.70.7 ng/dL, Anti-TPO Antibodies 850850 IU/mL
Profile 3: TSH 0.020.02 μ\mu U/mL, Free T4 3.23.2 ng/dL, 24-hour RAIU 68%68\% (diffuse pattern)
Profile 4: TSH 0.80.8 μ\mu U/mL, Free T4 1.11.1 ng/dL, Total T3 6565 ng/dL, Reverse T3 4545 ng/dL (Elevated)

Matches

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Answer

Profile 1 matches with Destructive thyroiditis; Profile 2 matches with Hashimoto thyroiditis; Profile 3 matches with Graves disease; Profile 4 matches with Euthyroid sick syndrome.
Each laboratory profile specifically aligns with one distinct pathophysiological mechanism: hormone leakage without synthesis (Profile 1), autoimmune gland destruction leading to failure (Profile 2), autoimmune continuous stimulation (Profile 3), and adaptive peripheral hormone diversion during illness (Profile 4).

Step-by-Step Solution

1
Evaluate the primary thyroid axis via TSH and Free T4.
Profiles 1 and 3 indicate primary hyperthyroidism (Low TSH, High Free T4). Profile 2 indicates primary hypothyroidism (High TSH, Low Free T4). Profile 4 indicates a euthyroid central state with an isolated low T3.
TSH and Free T4 establish the patient's baseline biochemical thyroid status.
2
Utilize secondary diagnostic markers (RAIU, antibodies, Reverse T3) to differentiate specific etiologies within each broad category.
Profile 1's low RAIU points to destructive release, while Profile 3's high RAIU points to active synthesis. Profile 2's antibodies confirm autoimmunity. Profile 4's elevated reverse T3 confirms altered peripheral metabolism.
Secondary tests distinguish between different pathophysiologic mechanisms that can cause similar TSH/Free T4 patterns.

Key Concept

Interpretation of thyroid function tests, radioactive iodine uptake, and peripheral thyroid hormone metabolism.
Question 1604Question →

A 4141-year-old woman comes to the primary care clinic for evaluation of joint pain and stiffness that began gradually over the past 33 months. She reports that the pain primarily affects her wrists and fingers on both hands. The stiffness is most pronounced upon awakening and typically takes about 22 hours to improve. She feels generally fatigued but denies fevers, weight loss, or skin rashes. Her vital signs are within normal limits. Physical examination demonstrates boggy swelling, warmth, and tenderness of the second and third metacarpophalangeal and proximal interphalangeal joints bilaterally. There is no erythema or joint deformity. A routine complete blood count obtained last week for a wellness visit showed a hemoglobin level of 11.2 g/dL11.2 \text{ g/dL} and a mean corpuscular volume of 88 fL88 \text{ fL}. Which of the following is the most appropriate next step in the diagnostic workup?

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Answer: Serologic testing for rheumatoid factor and anti-cyclic citrullinated peptide antibodies

Answer

Serologic testing for rheumatoid factor and anti-cyclic citrullinated peptide antibodies
The patient presents with classic signs and symptoms of rheumatoid arthritis, including insidious onset of symmetric polyarthritis involving the metacarpophalangeal and proximal interphalangeal joints, prolonged morning stiffness lasting more than one hour, and systemic symptoms like fatigue. The most appropriate initial diagnostic step is serologic testing for rheumatoid factor and anti-cyclic citrullinated peptide antibodies. Anti-cyclic citrullinated peptide antibodies are highly specific for rheumatoid arthritis and help confirm the diagnosis, while rheumatoid factor is sensitive but less specific.

Step-by-Step Solution

1
Identify the primary clinical syndrome from the patient's history and physical examination.
The patient has a chronic (greater than 6 weeks), symmetric inflammatory polyarthritis affecting the small joints of the hands, with prolonged morning stiffness.
Recognizing this classic pattern strongly suggests rheumatoid arthritis as the primary diagnosis.
2
Determine the most appropriate initial diagnostic modality.
Targeted laboratory serology is the standard next step to support the clinical diagnosis of rheumatoid arthritis.
Serologic testing provides specific diagnostic and prognostic information without the need for invasive procedures or expensive advanced imaging.
3
Select the specific laboratory tests indicated for this presentation.
Testing for rheumatoid factor and anti-cyclic citrullinated peptide antibodies is indicated.
These biomarkers are highly characteristic of rheumatoid arthritis and are essential components of the diagnostic criteria.

Key Concept

The initial diagnostic workup for a patient presenting with classic symptoms of rheumatoid arthritis (symmetric polyarthritis, prolonged morning stiffness) includes serologic testing for rheumatoid factor (RF) and anti-cyclic citrullinated peptide (anti-CCP) antibodies.
Question 1605Question →

An occupational health clinic evaluates a 38-year-old right-handed carpenter who reports chronic right forearm pain and hand numbness. The symptoms began approximately three months ago. He describes an aching discomfort in the proximal, anterior aspect of his forearm that worsens after extensive use of screwdrivers and heavy hand tools. He also notes tingling in his thumb, index finger, and middle finger. Unlike a colleague who recently underwent surgery for similar hand symptoms, the patient specifically denies being awakened from sleep by the pain. On physical examination, provocative testing with maximum passive wrist flexion (Phalen test) and tapping over the volar carpal ligament (Tinel sign) fail to reproduce the symptoms. However, resisted pronation of the forearm exacerbates the aching pain. Based on the most likely diagnosis, which of the following physical examination findings would distinguish this patient's condition from median nerve entrapment at the transverse carpal ligament?

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Answer: Decreased light touch sensation over the thenar eminence

Answer

Decreased light touch sensation over the thenar eminence
The correct physical examination finding is decreased light touch sensation over the thenar eminence. The patient's clinical presentation—proximal forearm pain exacerbated by resisted pronation, paresthesias in the thumb and index/middle fingers, absence of nocturnal pain, and negative Phalen and Tinel tests at the wrist—is classic for Pronator Teres syndrome. This condition involves entrapment of the median nerve between the two heads of the pronator teres muscle in the proximal forearm. A critical anatomical distinction between Pronator Teres syndrome and Carpal Tunnel Syndrome (CTS) is the involvement of the palmar cutaneous branch of the median nerve. This branch arises approximately 5 cm proximal to the transverse carpal ligament (flexor retinaculum) and travels superficial to the ligament to provide sensory innervation to the skin over the thenar eminence. Consequently, in CTS, the median nerve is compressed deep to the transverse carpal ligament, sparing the palmar cutaneous branch and preserving thenar sensation. In Pronator Teres syndrome, the median nerve is compressed proximally, affecting both the palmar cutaneous branch and the distal digital nerves. Therefore, decreased sensation over the thenar eminence distinguishes Pronator Teres syndrome from CTS.

Step-by-Step Solution

1
Analyze the clinical presentation.
The patient has proximal anterior forearm pain, paresthesias in the median nerve distribution (thumb, index, middle fingers), symptom exacerbation with resisted forearm pronation, absent nocturnal symptoms, and negative wrist provocative tests.
To formulate a differential diagnosis for median nerve distribution symptoms.
2
Differentiate between locations of median nerve entrapment.
The presentation strongly suggests Pronator Teres syndrome (compression between the heads of the pronator teres muscle) rather than Carpal Tunnel Syndrome (compression at the wrist).
Pronator Teres syndrome is characterized by proximal forearm pain exacerbated by pronation and a lack of classic Carpal Tunnel Syndrome signs like nocturnal awakening or positive Phalen/Tinel tests at the wrist.
3
Identify the key anatomical differentiator on physical examination.
The palmar cutaneous branch of the median nerve provides sensation to the thenar eminence. It branches off proximal to the transverse carpal ligament and travels superficially.
Because it travels superficial to the transverse carpal ligament, it is spared in Carpal Tunnel Syndrome. However, it is affected by proximal compressions such as Pronator Teres syndrome, resulting in thenar sensory loss.

Key Concept

The palmar cutaneous branch of the median nerve arises proximal to the transverse carpal ligament, supplying sensation to the thenar eminence; therefore, thenar sensory loss occurs in proximal median nerve entrapments (e.g., Pronator Teres syndrome) but is spared in Carpal Tunnel Syndrome.
Question 1606Question →

A 42-year-old man presents to the hospital with a 2-day history of low-grade fever, malaise, decreased urine output, and allograft tenderness. He underwent a deceased-donor kidney transplantation 2 months ago. His current medications include tacrolimus, mycophenolate mofetil, and prednisone. His serum creatinine has abruptly increased from a baseline of 1.3 mg/dL1.3 \text{ mg/dL} to 2.9 mg/dL2.9 \text{ mg/dL}. Initial laboratory studies show a subtherapeutic serum tacrolimus trough level. Urinalysis reveals mild proteinuria but is negative for infection.

Arrange the following steps in the most appropriate sequence for the continued evaluation and management of this patient's allograft dysfunction, from initial structural evaluation to the escalation of therapy for refractory immunologic disease.

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Answer

The correct sequence is to first perform a renal allograft Doppler ultrasound, followed by a percutaneous renal allograft biopsy, then administer pulse-dose intravenous methylprednisolone, and finally administer intravenous anti-thymocyte globulin if the condition is refractory.
The proper sequence begins with excluding non-immunologic causes of acute kidney injury. A Doppler ultrasound is noninvasive and effectively rules out vascular thrombosis or urinary obstruction. Once anatomical causes are excluded, a percutaneous renal biopsy is performed to establish a definitive histologic diagnosis. With the diagnosis confirmed, first-line therapy with pulse-dose intravenous corticosteroids is initiated to suppress T-lymphocyte activity. If the patient's allograft function does not improve, therapy is escalated to include T-cell depleting agents like anti-thymocyte globulin.

Step-by-Step Solution

1
Evaluate for structural or vascular abnormalities
Renal allograft Doppler ultrasound is performed.
Anatomic causes of acute kidney injury must be excluded noninvasively before an invasive biopsy is attempted.
2
Establish a definitive tissue diagnosis
A percutaneous renal allograft biopsy is obtained.
Histopathologic evaluation is required to confirm acute cellular rejection and guide targeted immunosuppressive therapy.
3
Initiate first-line treatment for acute cellular rejection
Pulse-dose intravenous methylprednisolone is administered.
High-dose corticosteroids are the standard initial therapy for acute cellular rejection.
4
Escalate treatment for refractory rejection
Intravenous anti-thymocyte globulin is administered.
Lymphocyte-depleting agents are reserved for patients who do not respond adequately to initial corticosteroid therapy.

Key Concept

The diagnostic workup for acute renal allograft dysfunction follows a stepwise approach: ruling out structural/vascular etiologies, confirming immunopathologic diagnosis with biopsy, initiating targeted therapy with corticosteroids, and escalating to depleting antibodies if refractory.
Question 1607Question →

A 6262-year-old postmenopausal woman is evaluated in the clinic after a routine comprehensive metabolic panel revealed an incidentally elevated serum total calcium of 11.5 mg/dL11.5 \text{ mg/dL}. She has a remote history of nephrolithiasis but currently feels well. She takes no medications and does not use over-the-counter supplements. The physician initiates a stepwise diagnostic and pre-operative evaluation pathway.

Arrange the following diagnostic evaluations in the most appropriate, evidence-based sequential order to establish the definitive etiology and complete the pre-operative workup.

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Answer

The correct sequence is: 1) Repeat calcium with albumin or ionized calcium, 2) Intact PTH, 3) 24-hour urine calcium, 4) DEXA scan, 5) Sestamibi scintigraphy.
The diagnostic workup for hypercalcemia follows a strict sequential algorithm to ensure accurate diagnosis and prevent unnecessary procedures. The first step is to confirm true hypercalcemia by repeating the measurement with a concurrent albumin level (to calculate corrected calcium) or by measuring ionized calcium. Once confirmed, the critical branch point is measuring intact parathyroid hormone (iPTH) to determine if the process is PTH-dependent. If iPTH is elevated or inappropriately normal, primary hyperparathyroidism is highly suspected, but familial hypocalciuric hypercalcemia (FHH) must be excluded next using a 24-hour urine calcium collection. Only after primary hyperparathyroidism is biochemically confirmed should the clinician assess for asymptomatic surgical indications (such as osteoporosis via a DEXA scan). Finally, pre-operative localization imaging, such as sestamibi scintigraphy, is indicated strictly as the last step to guide the surgeon, not as a primary diagnostic modality.

Step-by-Step Solution

1
Confirm the presence of true hypercalcemia.
Order a repeat total calcium with albumin or an ionized calcium level.
Total serum calcium can be falsely elevated due to hemoconcentration or abnormal protein binding. True hypercalcemia must be definitively verified before initiating a costly workup.
2
Determine if the hypercalcemia is parathyroid-mediated.
Measure the intact parathyroid hormone (iPTH) level.
The iPTH level distinguishes parathyroid-dependent etiologies (e.g., primary hyperparathyroidism, where iPTH is high or inappropriately normal) from parathyroid-independent etiologies (e.g., malignancy, vitamin D toxicity, where iPTH is suppressed).
3
Rule out familial hypocalciuric hypercalcemia (FHH).
Measure 24-hour urine calcium and creatinine excretion.
Primary hyperparathyroidism and FHH both present with hypercalcemia and elevated iPTH. A 24-hour urine calcium test differentiates them; FHH typically shows low calcium clearance (<100 mg/day< 100 \text{ mg/day}), while primary hyperparathyroidism shows normal or high clearance.
4
Assess for surgical indications in an asymptomatic patient.
Perform a bone mineral density assessment via DEXA scan.
Once primary hyperparathyroidism is biochemically established, an asymptomatic patient must be evaluated for end-organ damage (osteoporosis) to determine if surgical intervention (parathyroidectomy) is indicated.
5
Perform pre-operative anatomical localization.
Order a sestamibi scan and/or neck ultrasound.
Localization imaging should only be ordered after a biochemical diagnosis is made and the decision to proceed with surgery is finalized. It is not a diagnostic test; its sole purpose is to guide the surgical approach.

Key Concept

Diagnostic algorithm and sequential laboratory testing for hypercalcemia and primary hyperparathyroidism.
Estimated Time:2m 0s
Question 1608Question →

A 6666-year-old man presents to the internal medicine clinic for a routine health maintenance visit. He reports a six-month history of mild urinary urgency, frequency, and nocturia, but denies any weight loss, bone pain, hematuria, or dysuria. He has no significant past medical history. Examination reveals a slightly enlarged, firm, and asymmetric prostate. As part of a comprehensive evaluation for a potential neoplastic process of the prostate, the physician considers the appropriate diagnostic and therapeutic algorithm.

Arrange the following diagnostic and management steps in the most appropriate chronological order according to current oncologic guidelines.

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Answer

The correct sequence begins with initial screening (PSA and DRE), followed by imaging (multiparametric MRI) to identify biopsy targets, tissue sampling (core needle biopsy), histopathologic evaluation (Gleason scoring), and finally, determining the definitive management plan.
The standard of care for evaluating a potential prostate neoplasm begins with establishing clinical suspicion via PSA and DRE. Because systematic random biopsies have a high false-negative rate, modern oncologic guidelines stipulate obtaining a multiparametric MRI next to identify specific high-risk targets. Once a target is identified, an ultrasound-guided core needle biopsy (often fusing the MRI images) is performed. The resulting tissue is pathologically analyzed to assign a Gleason score. Only after the histologic grade and stage are fully characterized can a definitive management plan, such as active surveillance or surgery, be safely initiated.

Step-by-Step Solution

1
Measure serum prostate-specific antigen (PSA) and perform a digital rectal examination (DRE).
Establishes initial clinical suspicion and risk level for a prostatic neoplasm.
Non-invasive baseline screening must be performed to justify further advanced imaging or invasive procedures.
2
Obtain a multiparametric MRI (mpMRI) of the prostate.
Locates discrete, suspicious intraprostatic lesions and assigns a PI-RADS score.
Performing an MRI before a biopsy increases the detection of clinically significant cancers and allows for precise targeting.
3
Perform a targeted, ultrasound-guided core needle biopsy.
Procures direct tissue samples from the suspected neoplastic lesions.
Histologic material is required to confirm the presence of malignant cells.
4
Analyze the histopathologic specimens for a Gleason score.
Determines the histologic grade and biologic aggressiveness of the cancer.
Tumor grade is a critical prognostic factor that dictates appropriate treatment pathways.
5
Initiate definitive management.
Provides appropriate oncologic care (e.g., active surveillance or surgery).
Therapy must be tailored to the confirmed diagnosis and risk stratification established in the previous steps.

Key Concept

Sequential diagnostic and staging algorithm for prostate cancer, prioritizing non-invasive imaging prior to biopsy.
Question 1609Question →

A 72-year-old woman is brought to the emergency department by emergency medical services. Her family reports that she was last seen in her normal state of health at 10:00 PM the previous night. She awoke at 6:00 AM today with profound left-sided hemiparesis, rightward gaze deviation, and severe dysarthria. Her current blood pressure is 170/90 mmHg, and point-of-care blood glucose is 110 mg/dL. The institutional acute stroke code is activated. Arrange the following neuroimaging modalities in the standard step-wise sequence to evaluate this patient's eligibility for and to execute endovascular reperfusion therapy.

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Answer

The correct sequential order is: 1. Non-contrast CT (NCCT), 2. CT Angiography (CTA), 3. CT Perfusion (CTP), 4. Digital Subtraction Angiography (DSA).
The evaluation of an acute wake-up stroke with severe deficits requires a highly standardized step-wise imaging protocol. The absolute first priority is ruling out a hemorrhage with a Non-contrast CT. Once excluded, a CTA is reviewed to detect a large vessel occlusion (LVO). Because the patient is outside the standard 4.5-hour thrombolytic window, advanced imaging with CT Perfusion must then be analyzed to ensure there is a salvageable ischemic penumbra. Finally, if criteria are met, the patient is taken for Digital Subtraction Angiography, which serves as the diagnostic roadmap for endovascular mechanical thrombectomy.

Step-by-Step Solution

1
Exclude acute intracranial hemorrhage and assess for extensive early infarction.
Non-contrast CT (NCCT) of the head is acquired and interpreted first.
Thrombolytic and endovascular therapies are absolutely contraindicated in the presence of hemorrhage; NCCT is the fastest and most reliable initial test for this purpose.
2
Identify the presence of a proximal large vessel occlusion (LVO).
Computed tomography angiography (CTA) of the head and neck is performed.
Patients with LVOs (e.g., middle cerebral artery or internal carotid artery) are candidates for mechanical thrombectomy, making non-invasive vascular imaging the next logical requirement.
3
Assess the ratio of infarcted tissue to salvageable tissue.
Computed tomography perfusion (CTP) of the brain is analyzed.
Because this is a wake-up stroke with symptom onset potentially greater than 6 hours ago, evidence of a favorable target mismatch (small core, large penumbra) is required by clinical criteria before proceeding to late-window thrombectomy.
4
Perform definitive visualization and therapeutic intervention.
Digital subtraction angiography (DSA) is executed.
Catheter-based DSA is the gold standard imaging modality used to precisely navigate the cerebral vasculature and perform the mechanical thrombectomy procedure.

Key Concept

Standardized sequential interpretation of neuroimaging in acute extended-window ischemic stroke.
Estimated Time:1m 30s
Question 1610Question →

An outpatient evaluation is conducted for a 26-year-old female who reports a lifelong history of recurrent epistaxis and menorrhagia. Her menstrual periods typically last 88 to 1010 days and require changing a highly absorbent pad every 22 hours. One month ago, she required suturing and localized thrombin application for persistent oozing following a routine dental extraction. The patient takes an oral contraceptive pill and an over-the-counter iron supplement. Family history is notable for a mother who underwent a hysterectomy at age 4040 for heavy uterine bleeding.

Vital signs are normal. Physical examination reveals scattered, small ecchymoses on the shins but is otherwise unremarkable; there are no petechiae or joint effusions.

Initial laboratory studies reveal:
Complete blood count:
Hemoglobin: 10.8 g/dL10.8 \text{ g/dL}
Mean corpuscular volume: 76 fL76 \text{ fL}
Platelet count: 285,000/μL285,000 /\mu\text{L}

Coagulation profile:
Prothrombin time (PT): 12.5 seconds12.5 \text{ seconds} (Reference: 11−15 seconds11-15 \text{ seconds})
Activated partial thromboplastin time (aPTT): 52 seconds52 \text{ seconds} (Reference: 25−40 seconds25-40 \text{ seconds})
aPTT mixing study (1:1 with normal plasma): 31 seconds31 \text{ seconds}

Further hemostatic testing:
Platelet Function Analyzer (PFA-100) closure times:
Collagen/Epinephrine: 185 seconds185 \text{ seconds} (Reference: 84−160 seconds84-160 \text{ seconds})
Collagen/ADP: 142 seconds142 \text{ seconds} (Reference: 68−121 seconds68-121 \text{ seconds})
Factor VIII activity: 35%35\% (Reference: 50−150%50-150\%)

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

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Answer: von Willebrand disease

Answer

von Willebrand disease
The correct answer is von Willebrand disease because it uniquely bridges primary and secondary hemostatic defects. von Willebrand factor (vWF) serves two critical roles: it mediates platelet adhesion to damaged endothelium (accounting for the mucosal bleeding and prolonged PFA-100) and it acts as a carrier protein that protects Factor VIII from rapid proteolytic degradation in the circulation. A deficiency in vWF therefore leads to mildly reduced Factor VIII levels, causing an isolated prolongation of the aPTT that fully corrects when missing factors are supplied via a 1:1 mixing study with normal plasma.

Step-by-Step Solution

1
Analyze the clinical presentation and initial laboratory results to identify the bleeding pattern.
The patient has a history of mucocutaneous bleeding (epistaxis, menorrhagia) indicating a primary hemostasis defect, alongside a prolonged aPTT indicating an intrinsic pathway coagulation defect.
Identifying whether bleeding is due to primary hemostasis (platelet/vessel wall) or secondary hemostasis (coagulation cascade) narrows the differential diagnosis.
2
Interpret the 1:1 mixing study results.
The prolonged aPTT of 52 seconds corrects to 31 seconds (normal) when mixed with normal plasma.
A corrected mixing study indicates a coagulation factor deficiency rather than the presence of an inhibitor (such as a lupus anticoagulant or acquired factor inhibitor).
3
Synthesize the PFA-100, Factor VIII, and mixing study findings to establish the final diagnosis.
The patient has abnormal platelet function (prolonged PFA-100) despite normal platelet numbers, combined with reduced Factor VIII activity.
von Willebrand factor (vWF) is required for both platelet adhesion (primary hemostasis) and the stabilization of Factor VIII in the plasma (secondary hemostasis). A deficiency in vWF perfectly explains the dual defect.

Key Concept

von Willebrand disease characteristically presents with both a primary hemostatic defect (prolonged PFA-100 or bleeding time) and a secondary hemostatic defect (prolonged aPTT that corrects on mixing study due to low Factor VIII stabilization).
Question 1611Question →

A 62-year-old woman is evaluated in the gastroenterology clinic for progressive fatigue, lower extremity paresthesias, and a burning sensation in her tongue. Laboratory testing reveals a hemoglobin level of 9.2 g/dL and a mean corpuscular volume of 114 fL. An upper gastrointestinal endoscopy is performed, revealing a thinned, featureless mucosa in the gastric body and fundus, with preservation of the normal rugal architecture in the gastric antrum. Random biopsies are obtained. The synoptic pathology report indicates the following:

Gastric body and fundus: Marked loss of specialized oxyntic glands with extensive replacement by intestinal-type epithelium containing goblet cells. The lamina propria contains a dense lymphoplasmacytic inflammatory infiltrate. Immunohistochemical staining for chromogranin A demonstrates nodular hyperplasia of neuroendocrine cells.

Gastric antrum: Unremarkable foveolar epithelium and mucinous glands. No acute inflammation is present, and immunostains for *Helicobacter* species are negative.

Which of the following is the most likely diagnosis based on these clinicopathologic findings?

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Answer: Autoimmune metaplastic atrophic gastritis

Answer

Autoimmune metaplastic atrophic gastritis
The correct diagnosis is autoimmune metaplastic atrophic gastritis (AMAG). AMAG is mediated by CD4+ T-cell destruction of parietal cells, leading to profound loss of oxyntic glands in the body and fundus. The resulting achlorhydria stimulates antral G-cells to overproduce gastrin. This prolonged hypergastrinemia trophic effect on enterochromaffin-like (ECL) cells leads to their linear or nodular hyperplasia, as highlighted by chromogranin A staining. The antrum remains pathologically spared, differentiating it from other causes of chronic gastritis. The clinical presentation of macrocytic anemia and paresthesias correlates perfectly with the resulting vitamin B12 deficiency (pernicious anemia) due to intrinsic factor loss.

Step-by-Step Solution

1
Analyze the clinical presentation.
The patient has macrocytic anemia and neurologic symptoms (paresthesias), consistent with vitamin B12 deficiency (pernicious anemia).
Identifying the underlying clinical syndrome helps guide the interpretation of the histopathologic findings.
2
Evaluate the topographic distribution of the endoscopic and biopsy findings.
Pathology is restricted to the gastric body and fundus (thinned mucosa, glandular atrophy), while the antrum is entirely spared.
Topographic distribution is a key differentiator between etiologies of gastritis; autoimmune gastritis strictly involves the oxyntic mucosa (body/fundus) and spares the antrum.
3
Interpret the specific histopathologic and immunohistochemical features.
There is a dense lymphoplasmacytic infiltrate, oxyntic gland atrophy, intestinal metaplasia, and nodular ECL cell hyperplasia (chromogranin A positive).
These findings represent the complete histologic picture of end-stage autoimmune metaplastic atrophic gastritis. The destruction of parietal cells causes achlorhydria, triggering reflex hypergastrinemia which drives the ECL cell hyperplasia.

Key Concept

Autoimmune metaplastic atrophic gastritis presents with body- and fundus-restricted oxyntic gland atrophy, intestinal metaplasia, and neuroendocrine (ECL) cell hyperplasia secondary to achlorhydria-induced hypergastrinemia, while strictly sparing the gastric antrum.
Question 1612Question →

A 32-year-old woman is evaluated for a 6-month history of fatigue, loose stools, and an intensely pruritic, vesicular rash symmetrically distributed over her elbows and knees. Laboratory studies reveal a microcytic anemia, and serologic testing is markedly positive for anti-tissue transglutaminase IgA antibodies. The patient subsequently undergoes an esophagogastroduodenoscopy with biopsy of the distal duodenum, as well as a punch biopsy of perilesional skin. Which of the following histopathologic and immunofluorescence findings are most likely to be present in this patient's biopsy specimens? (Select all that apply)

Select all that apply

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Answer: Crypt hyperplasia with villous blunting and intraepithelial lymphocytosis; Granular IgA deposition localized to the tips of the dermal papillae

Answer

The correct biopsy findings are crypt hyperplasia with villous blunting and intraepithelial lymphocytosis in the duodenum, alongside granular IgA deposition localized to the tips of the dermal papillae in the skin.
The patient's clinical presentation of chronic diarrhea, microcytic anemia, positive anti-tissue transglutaminase IgA antibodies, and an intensely pruritic vesicular rash on extensor surfaces is highly characteristic of celiac disease with associated dermatitis herpetiformis. To establish the diagnosis definitively, biopsies are obtained. A duodenal biopsy in active celiac disease classically demonstrates crypt hyperplasia, partial or complete villous blunting (atrophy), and a prominent increase in intraepithelial lymphocytes. Concurrently, a perilesional skin biopsy in dermatitis herpetiformis will reveal the pathognomonic finding of granular IgA deposits localized to the tips of the dermal papillae on direct immunofluorescence.

Step-by-Step Solution

1
Analyze the clinical presentation and serology.
The patient has chronic diarrhea, microcytic anemia, and positive anti-tissue transglutaminase IgA, strongly pointing to celiac disease.
Identifying the underlying systemic disease is the first step in predicting the expected biopsy results.
2
Correlate the skin findings with the systemic diagnosis.
The intensely pruritic vesicular rash on extensor surfaces (elbows, knees) in a patient with celiac disease is clinically diagnostic of dermatitis herpetiformis.
Dermatitis herpetiformis is the cutaneous manifestation of celiac disease.
3
Determine the expected histopathology and immunofluorescence for these conditions.
Celiac disease shows duodenal villous blunting, crypt hyperplasia, and intraepithelial lymphocytes. Dermatitis herpetiformis shows granular IgA at the dermal papillary tips.
Matching the clinical diagnoses to their pathognomonic histologic and immunologic markers establishes the correct answers.

Key Concept

Celiac disease and Dermatitis Herpetiformis pathology
Estimated Time:1m 30s
Question 1613Question →

A group of medical residents is reviewing classic abdominal physical examination findings and their underlying pathophysiological or anatomic mechanisms. Match each eponymous physical examination sign with the mechanism that best explains its clinical presentation.

Click a left item, then click its matching right item

Items

Cullen sign
Kehr sign
Murphy sign
Courvoisier sign
Rovsing sign

Matches

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Answer

Cullen sign matches with extravasation of hemorrhagic exudate to periumbilical tissue; Kehr sign matches with C3-C5 nerve root mediated diaphragmatic irritation; Murphy sign matches with descent of an inflamed hepatobiliary structure during inspiration; Courvoisier sign matches with malignant obstruction of the common bile duct causing painless distention; Rovsing sign matches with transmission of localized pressure stretching the right-sided parietal peritoneum.
Each physical examination sign represents a distinct anatomical or pathophysiological process. Cullen sign is periumbilical ecchymosis due to tracking of retroperitoneal or intraperitoneal hemorrhage along fascial planes. Kehr sign is left shoulder pain referred via the phrenic nerve from irritation of the inferior surface of the diaphragm, classic for splenic rupture. Murphy sign is an inspiratory arrest caused by an inflamed gallbladder descending during respiration to meet the palpating hand. Courvoisier sign is a palpable, non-tender gallbladder caused by chronic, malignant obstruction of the common bile duct. Rovsing sign relies on the transmission of manual pressure from the left lower quadrant across the abdominal cavity, irritating the inflamed right-sided parietal peritoneum overlying the appendix.

Step-by-Step Solution

1
Analyze each eponymous physical examination sign to determine its clinical definition and presentation.
Identified the signs: Cullen (periumbilical ecchymosis), Kehr (referred left shoulder pain), Murphy (inspiratory arrest on right upper quadrant palpation), Courvoisier (palpable painless gallbladder with jaundice), and Rovsing (right lower quadrant pain elicited upon left lower quadrant palpation).
Accurate definition of the eponymous signs is required before mapping them to their underlying physiology.
2
Correlate each defined physical sign with its underlying pathophysiological or anatomical mechanism.
Mapped the corresponding anatomical pathways: retroperitoneal tracking to periumbilical area (Cullen), phrenic nerve referral (Kehr), diaphragmatic excursion (Murphy), distal malignant obstruction (Courvoisier), and indirect pressure transmission across the abdomen (Rovsing).
Understanding the anatomical mechanism allows for accurate diagnostic interpretation of physical findings in clinical practice.

Key Concept

Physical Examination Findings and their Pathophysiological Mechanisms
Question 1614Question →

A 62-year-old man comes to the clinic for a routine follow-up. He has a 10-year history of type 2 diabetes mellitus and a history of heart failure with preserved ejection fraction (ejection fraction of 55%55\%). His current medications include metformin, lisinopril, and amlodipine. He feels well and reports no shortness of breath, orthopnea, or lower extremity edema. His blood pressure is 128/78 mm Hg128/78 \text{ mm Hg}, and his pulse is 72/min72/\text{min}. Physical examination reveals clear lungs bilaterally and no jugular venous distention. Laboratory evaluation shows a hemoglobin A1c of 8.6%8.6\%. The physician considers adding pioglitazone to the patient's regimen to improve glycemic control but decides against it due to the patient's cardiac history. Which of the following best describes the cellular mechanism by which the avoided medication promotes fluid retention?

Show answer & explanation

Answer: Upregulation of epithelial sodium channel transcription in the renal collecting tubules

Answer

The avoided medication promotes fluid retention via the upregulation of epithelial sodium channel transcription in the renal collecting tubules.
Pioglitazone is a thiazolidinedione (TZD) that exerts its pharmacological effects by binding to and activating the peroxisome proliferator-activated receptor-gamma (PPAR-\gamma), an intracellular nuclear transcription factor. While its primary therapeutic effect is improving insulin sensitivity in adipose tissue and skeletal muscle, PPAR-\gamma receptors are also abundantly expressed in the principal cells of the renal collecting tubules. Activation of these receptors in the kidney increases the transcription and expression of the epithelial sodium channel (ENaC) and the basolateral Na+/K+-ATPase. This leads to significantly increased sodium reabsorption and subsequent water retention. The resulting intravascular volume expansion increases cardiac preload, which can precipitate or exacerbate congestive heart failure. For this reason, TZDs are strictly contraindicated in patients with symptomatic heart failure.

Step-by-Step Solution

1
Identify the medication class being considered and rejected.
The physician considered pioglitazone, a thiazolidinedione (TZD), but rejected it due to the patient's history of heart failure.
Recognizing the drug and its primary contraindication is required to understand which metabolic mechanism is being tested.
2
Recall the cellular target of thiazolidinediones.
TZDs bind to and activate the peroxisome proliferator-activated receptor-gamma (PPAR-\gamma), a nuclear transcription factor.
The question asks for the cellular mechanism leading to the specific side effect of fluid retention.
3
Determine how PPAR-\gamma activation leads to fluid retention.
PPAR-\gamma receptors in the renal collecting ducts stimulate the transcription of the epithelial sodium channel (ENaC), increasing renal sodium and water reabsorption.
Connecting the molecular target to the organ-specific physiological response explains the mechanism of the contraindication.

Key Concept

Mechanism of thiazolidinedione-induced fluid retention and heart failure exacerbation
Question 1615Question →

A previously healthy individual in their early forties presents to the urgent care clinic complaining of sudden-onset, sharp left lower quadrant abdominal pain that started 24 hours ago. The pain is localized and exacerbates with movement. Vital signs are within normal limits, and the patient is afebrile. Physical examination reveals focal tenderness in the left lower quadrant without guarding or rebound tenderness. Laboratory studies, including a complete blood count and basic metabolic panel, are unremarkable. A computed tomography (CT) scan of the abdomen and pelvis with intravenous contrast is performed. The radiologist notes an isolated, 2.5-cm, oval-shaped, fat-attenuating lesion abutting the anterior serosal surface of the sigmoid colon. The lesion features a hyperdense peripheral rim and a central high-attenuation dot. The adjacent colonic wall thickness is normal, and there is no free fluid or significant lymphadenopathy. Based on these imaging findings, which of the following best describes the underlying pathophysiology of this patient's acute presentation?

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Answer: Ischemic necrosis of an adipose appendage of the colon

Answer

Ischemic necrosis of an adipose appendage of the colon
The correct answer accurately describes the pathophysiology of epiploic appendagitis. Epiploic appendages are small, fat-filled pouches of visceral peritoneum that line the colon. When one of these appendages undergoes torsion, it leads to venous thrombosis and subsequent ischemic necrosis. The CT findings described in the vignette are pathognomonic for this condition: the oval, fat-attenuating lesion represents the infarcted appendage, the hyperdense rim represents the inflamed surrounding visceral peritoneum, and the central high-attenuation dot represents the thrombosed central draining vein. Recognizing this specific imaging pattern is crucial because epiploic appendagitis is a benign, self-limiting condition managed conservatively with pain control, avoiding unnecessary antibiotics or surgery.

Step-by-Step Solution

1
Analyze the clinical presentation.
The patient has acute left lower quadrant pain but lacks systemic inflammatory signs (normal vital signs, afebrile, normal leukocyte count), suggesting a localized, possibly non-infectious etiology.
Establishing the clinical severity and systemic involvement helps differentiate between inflammatory, infectious, and ischemic causes of abdominal pain.
2
Interpret the specific computed tomography (CT) imaging findings.
The CT shows an oval, fat-attenuating lesion with a hyperdense peripheral rim and a central high-attenuation dot adjacent to a normal-thickness colon.
Imaging is the definitive diagnostic modality for this presentation. The specific combination of radiological signs must be correlated with a structural pathology.
3
Synthesize the clinical and radiologic data to determine the pathophysiology.
The radiologic pattern is pathognomonic for epiploic appendagitis, which occurs due to torsion and subsequent ischemic necrosis of an epiploic appendage.
Recognizing this classic radiologic signature prevents misdiagnosis of conditions requiring surgical or antibiotic intervention, as epiploic appendagitis is treated conservatively with NSAIDs.

Key Concept

Radiologic identification of epiploic appendagitis
Question 1616Question →

Match each patient's clinical presentation with the single most appropriate initial or next imaging study to establish the diagnosis.

Click a left item, then click its matching right item

Items

A 28-year-old pregnant woman at 16 weeks gestation presents with acute dyspnea and pleuritic chest pain. Her chest radiograph is normal, and bilateral lower extremity venous ultrasound shows no deep vein thrombosis.
A 70-year-old man with a non-conditional permanent pacemaker presents with rapidly progressive bilateral lower extremity weakness, sensory loss below the umbilicus, and acute urinary retention.
A 55-year-old man presents with sudden-onset, severe, tearing chest pain radiating to the back. Examination shows asymmetric radial pulses. Laboratory testing reveals a serum creatinine of 3.8 mg/dL.
A 9-year-old girl presents with a 1-day history of periumbilical pain that has migrated to the right lower quadrant, accompanied by fever, nausea, and localized rebound tenderness.

Matches

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Answer

The pregnant patient with suspected pulmonary embolism matches with Ventilation-perfusion (V/Q) scan. The patient with suspected spinal cord compression and a pacemaker matches with CT myelography. The patient with suspected aortic dissection and acute kidney injury matches with Transesophageal echocardiography (TEE). The pediatric patient with suspected appendicitis matches with Graded compression ultrasonography.
Each correct match directly applies evidence-based guidelines for imaging selection while navigating a major patient-specific contraindication (e.g., pregnancy, severe kidney injury, non-compatible medical devices, and young age).

Step-by-Step Solution

1
Analyze the pregnant patient's presentation (acute dyspnea, pleuritic pain, normal chest radiograph, and negative lower extremity ultrasound).
Identify that the next best step is pulmonary imaging that strictly minimizes radiation exposure.
V/Q scan is preferred over CT pulmonary angiography in pregnancy when the initial chest radiograph is completely normal.
2
Evaluate the patient with acute spinal cord compression symptoms and a non-conditional pacemaker.
Determine that Magnetic Resonance Imaging (MRI) is absolutely contraindicated.
CT myelography provides the necessary visualization of the spinal canal and cord when an MRI cannot be safely performed.
3
Assess the patient with signs of acute aortic dissection and severe acute kidney injury.
Recognize that iodine-based contrast for CT angiography is contraindicated.
Transesophageal echocardiography (TEE) accurately diagnoses aortic dissection without the need for nephrotoxic contrast agents.
4
Consider the pediatric patient with classic symptoms of acute appendicitis.
Select an imaging modality that entirely avoids ionizing radiation.
Graded compression ultrasonography is the first-line imaging choice in children to adhere to radiation safety principles.

Key Concept

When ordering diagnostic imaging, the choice of modality must be strictly tailored to patient-specific contraindications, such as avoiding ionizing radiation in children and pregnant women, avoiding iodinated contrast in severe acute kidney injury, and avoiding MRI in patients with non-conditional metallic implants.
Estimated Time:1m 30s
Question 1617Question →

A 5555-year-old man visits his primary care physician to discuss the results of a recent imaging study. Two days ago, he was evaluated in the emergency department for severe, colicky left flank pain and was diagnosed with a 44-mm ureteral stone, which he has since passed. The unenhanced computed tomography (CT) scan of the abdomen and pelvis obtained during that visit confirmed the stone but also revealed an incidental 3.43.4-cm nodule in the right adrenal gland. The patient has a history of essential hypertension managed with lisinopril and amlodipine. He reports feeling well and denies headaches, palpitations, episodic sweating, or unexplained weight changes. His blood pressure today is 132/82132/82 mmHg, and his heart rate is 7676/min. The physician reviews the CT scan images and notes that the right adrenal mass is well-circumscribed and homogeneous. A region of interest placed over the mass reveals an attenuation value of 66 Hounsfield Units (HU). Based on the interpretation of these imaging findings, which of the following is the most appropriate next step in management?

Show answer & explanation

Answer: Biochemical evaluation for hormone hypersecretion

Answer

Biochemical evaluation for hormone hypersecretion
Adrenal incidentalomas are discovered in approximately 5%5\% to 7%7\% of abdominal CT scans. Evaluation focuses on two main goals: ruling out malignancy (via imaging) and ruling out autonomous hormone secretion (via biochemical testing). The most critical imaging parameter on an unenhanced CT scan is the attenuation value, measured in Hounsfield Units (HU). An unenhanced attenuation of <10< 10 HU is highly specific for a benign, lipid-rich adrenal adenoma. Because this patient's mass has an attenuation of 66 HU, the imaging definitively points to a benign lesion, and no further imaging characterization is required. However, regardless of how benign an incidentaloma appears on imaging, up to 15%15\% of these masses secrete hormones (such as cortisol, catecholamines, or aldosterone). Therefore, the correct next step is to perform a comprehensive biochemical evaluation. This typically includes a 11-mg overnight dexamethasone suppression test, plasma free metanephrines, and a plasma aldosterone-to-renin ratio (given his hypertension).

Step-by-Step Solution

1
Analyze the imaging findings provided in the stem.
The unenhanced CT shows a 3.43.4-cm homogeneous right adrenal mass with an attenuation of 66 HU.
To determine the malignant potential of the adrenal incidentaloma based on radiological criteria.
2
Interpret the clinical significance of the Hounsfield Units.
An unenhanced attenuation value of <10< 10 HU is highly specific for a lipid-rich adrenal adenoma, which is benign.
To decide whether further characterizing imaging (like a washout protocol or MRI) is necessary.
3
Determine the required management for a benign-appearing adrenal incidentaloma.
Proceed with biochemical testing to rule out pheochromocytoma, subclinical Cushing syndrome, and primary aldosteronism.
Up to 15%15\% of radiologically benign incidentalomas are functional and require medical or surgical intervention.

Key Concept

Adrenal Incidentaloma Management
Question 1618Question →

An occupational therapist in her mid-forties establishes care for persistent, generalized itching that is particularly bothersome at night. She also reports progressive exhaustion over the past several months despite getting adequate sleep. Physical examination reveals excoriations on her upper and lower extremities, but there is no scleral icterus, hepatosplenomegaly, or rash. Laboratory studies show a markedly elevated alkaline phosphatase and gamma-glutamyl transferase, with a normal total bilirubin level and mildly elevated aminotransferases. While awaiting an autoantibody panel, a percutaneous liver biopsy is performed to evaluate the etiology of her cholestasis. Microscopic evaluation of the specimen demonstrates a dense portal tract inflammatory infiltrate consisting of lymphocytes and plasma cells that is actively invading and destroying small interlobular bile ducts. Focal, poorly formed non-caseating granulomas are also identified immediately adjacent to the damaged ducts. There is minimal interface hepatitis and no significant parenchymal fibrosis.

Based on the clinicopathologic findings, which of the following is the most accurate diagnosis?

Show answer & explanation

Answer: Primary biliary cholangitis

Answer

Primary biliary cholangitis
The diagnosis is primary biliary cholangitis. The clinical presentation of fatigue and severe pruritus without jaundice in a middle-aged woman, combined with a cholestatic laboratory profile (elevated alkaline phosphatase and GGT), is highly suspicious for this condition. The definitive diagnostic feature on liver biopsy is the 'florid duct lesion,' which consists of a dense lymphoplasmacytic infiltrate and poorly formed non-caseating granulomas that actively invade and destroy the small interlobular bile ducts. This histopathologic finding is pathognomonic and confirms the diagnosis even before anti-mitochondrial antibody testing results are available.

Step-by-Step Solution

1
Analyze the patient's clinical presentation and initial laboratory findings.
The patient has pruritus, fatigue, and an isolated elevation in alkaline phosphatase and gamma-glutamyl transferase (GGT), indicating a cholestatic pattern of liver injury.
Establishing the clinical syndrome narrows the differential diagnosis primarily to biliary tract diseases or drug-induced cholestasis.
2
Interpret the histopathologic findings from the liver biopsy.
The biopsy shows granulomatous destruction of small interlobular bile ducts by a lymphoplasmacytic infiltrate, known as the 'florid duct lesion'.
Identifying the specific pattern of tissue injury on biopsy is required to differentiate among the various causes of intrahepatic cholestasis.
3
Synthesize the clinical and pathologic data to formulate the final diagnosis.
The combination of a cholestatic clinical picture in a middle-aged woman with pathognomonic florid duct lesions confirms primary biliary cholangitis.
Matching the biopsy hallmark with the demographic and laboratory profile provides a definitive diagnosis even before autoantibody (anti-mitochondrial antibody) results are available.

Key Concept

The pathologic hallmark of primary biliary cholangitis is the 'florid duct lesion', which is characterized by a dense lymphoplasmacytic infiltrate and granulomatous destruction of the small interlobular bile ducts.
Question 1619Question →

An internist is evaluating a 48-year-old man who reports a 3-month history of persistent nasal crusting, recurrent epistaxis, and migratory arthralgias. Over the past two weeks, the patient has developed a cough that occasionally produces blood-tinged sputum. He has no prior medical history and takes no medications. Vital signs are within normal limits except for a blood pressure of 152/94 mm Hg. Physical examination reveals an ulcerated septal mucosa and a saddle-nose deformity. Laboratory testing shows a blood urea nitrogen of 38 mg/dL and a serum creatinine of 2.6 mg/dL. Urinalysis demonstrates 2+ protein, numerous dysmorphic red blood cells, and red blood cell casts. Which of the following immunopathologic mechanisms is most directly responsible for this patient's renal findings?

Show answer & explanation

Answer: Neutrophil activation and degranulation triggered by autoantibodies against granule proteins

Answer

Neutrophil activation and degranulation triggered by autoantibodies against granule proteins
This patient's clinical triad of upper respiratory tract destruction (nasal ulceration, saddle-nose deformity), lower respiratory tract involvement (hemoptysis), and glomerulonephritis (RBC casts, elevated creatinine) is the classic presentation of Granulomatosis with polyangiitis (GPA). GPA is an antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis, most commonly involving anti-proteinase 3 (c-ANCA) autoantibodies. The pathogenesis involves circulating ANCAs binding to their target antigens on the surface of neutrophils that have been primed by inflammatory cytokines. This binding induces massive neutrophil activation, degranulation, and release of reactive oxygen species, which directly damage the adjacent vascular endothelium. In the kidney, this immune-mediated endothelial injury manifests as a pauci-immune necrotizing crescentic glomerulonephritis, producing the observed hematuria and red blood cell casts.

Step-by-Step Solution

1
Analyze the patient's clinical presentation.
The patient has upper respiratory tract involvement (nasal ulceration, saddle-nose deformity), lower respiratory tract involvement (hemoptysis), and rapidly progressive renal failure (elevated creatinine, RBC casts).
Identifying the specific pattern of affected organ systems is the first step in narrowing the differential diagnosis for systemic vasculitides.
2
Formulate a diagnosis based on the clinical triad.
The combination of upper respiratory, lower respiratory, and renal involvement is highly characteristic of Granulomatosis with polyangiitis (GPA).
GPA (formerly Wegener granulomatosis) classically presents with this triad and is strongly associated with c-ANCA (anti-proteinase 3 antibodies).
3
Identify the immunopathologic mechanism of the renal injury in this disease.
The renal pathology in GPA is a pauci-immune necrotizing crescentic glomerulonephritis. It is driven by circulating anti-neutrophil cytoplasmic antibodies (ANCAs) that bind and activate primed neutrophils, causing them to degranulate and damage the vascular endothelium.
Understanding the underlying molecular mechanism answers the specific question regarding the etiology of the renal findings.

Key Concept

Granulomatosis with polyangiitis (GPA) is a small-vessel vasculitis characterized by upper and lower respiratory tract necrotizing granulomas and a pauci-immune glomerulonephritis, mediated by ANCA-induced neutrophil activation.
Question 1620Question →

A 29-year-old woman, G1P0 at 24 weeks gestation, presents to the emergency department with sudden-onset shortness of breath and right-sided pleuritic chest pain. Her pulse is 112/min, respiratory rate is 24/min, and blood pressure is 110/70 mm Hg. Oxygen saturation is 96% on room air. Physical examination reveals clear lungs bilaterally and no asymmetric leg swelling. An electrocardiogram shows sinus tachycardia. You highly suspect an acute pulmonary embolism (PE).

Assuming each test fails to definitively rule in or rule out the diagnosis (i.e., yielding normal or indeterminate results), arrange the following imaging studies in the most appropriate step-by-step diagnostic sequence according to current evidence-based guidelines for suspected PE in pregnancy.

Drag items to arrange them in the correct order

Show answer & explanation

Answer

The correct sequence is: Chest radiography, followed by Bilateral lower extremity compression ultrasonography, then a Ventilation-perfusion (V/Q) scan, and finally Computed tomography pulmonary angiography (CTPA).
The correct diagnostic algorithm for suspected pulmonary embolism in a pregnant patient prioritizes minimizing radiation exposure to the fetus and the maternal breast tissue. The evaluation begins with a chest radiograph to rule out alternative cardiopulmonary pathology and guide subsequent testing. If the radiograph is normal, bilateral lower extremity compression ultrasonography is performed; finding a deep vein thrombosis (DVT) warrants immediate anticoagulation, safely concluding the diagnostic workup without further radiation. If ultrasonography is negative, definitive pulmonary imaging is required. A ventilation-perfusion (V/Q) scan is preferred over computed tomography pulmonary angiography (CTPA) in patients with a normal chest radiograph because it delivers significantly less radiation to the radiosensitive maternal breasts. Finally, if the V/Q scan yields a non-diagnostic or indeterminate result, CTPA must be performed as the ultimate definitive test to confirm or exclude a pulmonary embolism.

Step-by-Step Solution

1
Order a chest radiograph.
Rules out alternative pulmonary pathology (e.g., pneumonia, pneumothorax).
It is the safest initial imaging step with minimal fetal radiation. A normal result dictates that a V/Q scan should be the definitive pulmonary test, whereas an abnormal result favors proceeding directly to CTPA.
2
Perform bilateral lower extremity compression ultrasonography.
Evaluates for the presence of a deep vein thrombosis (DVT).
If positive, therapeutic anticoagulation is indicated, and the diagnostic pathway is safely halted to avoid exposing the fetus and maternal breasts to unnecessary radiation.
3
Order a ventilation-perfusion (V/Q) scan.
Provides definitive imaging of pulmonary perfusion and ventilation.
When both previous tests are negative and the chest radiograph is normal, a V/Q scan is prioritized over CTPA because it delivers a significantly lower dose of ionizing radiation to the highly radiosensitive maternal breast tissue.
4
Proceed with computed tomography pulmonary angiography (CTPA).
Definitively confirms or excludes a pulmonary embolism.
If the V/Q scan yields an indeterminate or non-diagnostic result, CTPA is mandatory as the final diagnostic step to ensure a life-threatening PE is not missed.

Key Concept

The diagnostic algorithm for suspected pulmonary embolism in pregnancy relies on a stepwise imaging approach designed to minimize ionizing radiation exposure, prioritizing tests with lower maternal breast and fetal radiation profiles.
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