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Difficulty: HardPathology and Biopsy Interpretation

A 42-year-old woman presents to the clinic with a 6-month history of progressive fatigue and severe, generalized pruritus. She has no significant past medical history and takes no over-the-counter or prescription medications. On physical examination, there is mild hepatomegaly and scattered excoriations on her extremities. Laboratory studies reveal:

Total bilirubin: 1.1 mg/dL
Alkaline phosphatase: 520 U/L
Aspartate aminotransferase (AST): 58 U/L
Alanine aminotransferase (ALT): 64 U/L
Antimitochondrial antibody (AMA): Negative
Antinuclear antibody (ANA): Positive (1:640)
Anti-smooth muscle antibody (ASMA): Positive (1:160)

Given the cholestatic enzyme pattern with complex serologies, a percutaneous liver biopsy is obtained. The pathology report describes portal tracts expanded by a dense mononuclear infiltrate predominantly composed of lymphocytes. There is asymmetric, non-suppurative destruction of interlobular septal bile ducts accompanied by occasional poorly formed granulomas. The limiting plate remains largely intact, and there is no significant interface hepatitis or lobular necroinflammation. Based on the biopsy findings and clinical presentation, which of the following is the most likely diagnosis?

  1. A
    Autoimmune hepatitis
  2. Primary biliary cholangitisAnswer
  3. C
    Primary sclerosing cholangitis
  4. D
    Autoimmune hepatitis-primary biliary cholangitis overlap syndrome
  5. E
    Hepatic sarcoidosis

Answer

Primary biliary cholangitis
The correct answer is Primary biliary cholangitis. This patient presents with classical clinical and biochemical features of a cholestatic liver disease (fatigue, pruritus, isolated alkaline phosphatase elevation). Although the classic hallmark of this disease is the antimitochondrial antibody (AMA), approximately 5% to 10% of patients are AMA-negative. These patients often possess positive ANA or ASMA titers, a variant historically referred to as autoimmune cholangitis. In the absence of positive AMA serology, the diagnosis hinges entirely on the liver biopsy. The histopathology described—a dense mononuclear portal infiltrate causing asymmetric, non-suppurative granulomatous destruction of interlobular bile ducts (the 'florid duct lesion') with an intact limiting plate—is unequivocally pathognomonic for this disease.

Step-by-Step Solution

1
Analyze the clinical presentation and laboratory profile.
The patient has a profound cholestatic pattern (elevated alkaline phosphatase, normal/mildly elevated aminotransferases) with pruritus, suggesting biliary tract pathology.
Establishing the primary pattern of liver injury (cholestatic vs. hepatocellular) dictates the differential diagnosis.
2
Evaluate the serologic markers in the context of the clinical picture.
The patient is AMA-negative (unusual for primary biliary cholangitis) but ANA and ASMA-positive (typically associated with autoimmune hepatitis).
Discordant or overlapping serologies in liver disease necessitate histopathologic evaluation to reach a definitive diagnosis.
3
Interpret the liver biopsy findings.
The biopsy shows non-suppurative destruction of interlobular bile ducts with granulomas (florid duct lesion) and an intact limiting plate (no interface hepatitis).
Histopathology is the gold standard for distinguishing autoimmune liver diseases. The presence of the florid duct lesion confirms primary biliary cholangitis, overriding the misleading serology.

Key Concept

The diagnosis of AMA-negative primary biliary cholangitis relies definitively on the histopathologic finding of non-suppurative granulomatous destruction of interlobular bile ducts without significant interface hepatitis.
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Topics

Pathology and Biopsy Interpretation

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