A 48-year-old female patient is evaluated in the acute care clinic for a 4-day history of … — USMLE Step 3

A 48-year-old female patient is evaluated in the acute care clinic for a 4-day history of worsening right-sided upper abdominal discomfort, nausea, malaise, and dark-colored urine. She notes feeling feverish at home. Her medical history is significant for severe seropositive rheumatoid arthritis. Due to inadequate symptom control, she was transitioned to a regimen including infliximab 12 weeks ago, alongside her longstanding methotrexate therapy. Vital signs show a temperature of $37.9^\circ\text{C}$ ( $100.2^\circ\text{F}$ ), blood pressure of 112/68 mmHg, and heart rate of 92/min. Examination is notable for yellowing of the sclerae and moderate tenderness to palpation in the right upper quadrant without rebound or guarding.

Laboratory studies demonstrate:

Laboratory Test	Result	Reference Range
Total bilirubin	4.8 mg/dL	0.1 - 1.2 mg/dL
Direct bilirubin	3.5 mg/dL	0.0 - 0.3 mg/dL
Alanine aminotransferase (ALT)	2,100 U/L	10 - 40 U/L
Aspartate aminotransferase (AST)	1,850 U/L	10 - 40 U/L
Alkaline phosphatase	180 U/L	40 - 120 U/L
Amylase	55 U/L	30 - 110 U/L

Based on the clinical and laboratory presentation, which of the following is the most likely etiology of this patient's acute illness?

A
Acute ascending cholangitis
B
Methotrexate hepatotoxicity
Hepatitis B virus reactivationAnswer
D
Acute calculous cholecystitis
E
Drug-induced hemolytic anemia

Answer

Hepatitis B virus reactivation

The correct answer is Hepatitis B virus reactivation. This patient presents with acute liver injury characterized by marked transaminitis (ALT and AST > 1000 U/L) and direct hyperbilirubinemia. This pattern is indicative of severe hepatocellular damage (e.g., viral hepatitis, ischemic hepatitis, or toxin-induced hepatitis) rather than a cholestatic process. The recent initiation of infliximab, a tumor necrosis factor (TNF)-alpha inhibitor, places her at high risk for reactivation of latent viral infections. Hepatitis B virus (HBV) reactivation is a well-documented, classic, and potentially fatal complication of TNF-alpha inhibitor therapy. Patients must be screened for HBV prior to starting these biologics. The timeline of 12 weeks post-initiation perfectly aligns with the reactivation period, leading to acute fulminant hepatitis.

Step-by-Step Solution

Analyze the patient's presenting clinical symptoms.

The patient exhibits a triad of fever, right upper quadrant abdominal pain, and jaundice (scleral icterus, dark urine).

This establishes a broad differential diagnosis focused on acute hepatobiliary disease.

Interpret the laboratory findings to narrow the differential.

Labs show a conjugated hyperbilirubinemia and profoundly elevated transaminases (ALT/AST > 1000 U/L) with only mildly elevated alkaline phosphatase.

This specific lab pattern confirms a severe acute hepatocellular injury rather than a primary cholestatic (biliary) process like cholangitis.

Synthesize the hepatocellular injury pattern with the patient's medication history.

The patient was started on infliximab (a TNF-alpha inhibitor) 12 weeks ago, which perfectly aligns with the incubation/reactivation timeline for latent viral hepatitis.

Identifying the immunomodulatory trigger confirms the etiology, as TNF-alpha inhibitors carry a high risk of precipitating fatal Hepatitis B reactivation.

Key Concept

Formulating a differential diagnosis for acute liver injury requires distinguishing a hepatocellular pattern (ALT/AST >1000 U/L) from a cholestatic pattern, and recognizing that initiating TNF-alpha inhibitors carries a high risk for fatal Hepatitis B virus reactivation.

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