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Difficulty: MediumPathology and Biopsy Interpretation

A 4242-year-old man comes to the clinic for evaluation of chronic fatigue, mild exertional dyspnea, and recently discovered elevated liver enzymes. He has no history of alcohol use, intravenous drug use, or unprotected sexual intercourse. His body mass index is 23 kg/m223 \text{ kg/m}^2. Laboratory testing shows an aspartate aminotransferase (AST) of 85 U/L85 \text{ U/L} and an alanine aminotransferase (ALT) of 92 U/L92 \text{ U/L}. Serum alkaline phosphatase, total bilirubin, and viral hepatitis serologies are unremarkable. A percutaneous liver biopsy is performed to evaluate the unexplained transaminitis. Microscopic examination of the hepatic parenchyma reveals the presence of intracytoplasmic, round, eosinophilic inclusions predominantly within periportal hepatocytes. These inclusions stain strongly positive with periodic acid-Schiff (PAS) and resist digestion by diastase. Which of the following is the most likely diagnosis based on these histopathologic findings?

  1. A
    Alcoholic steatohepatitis
  2. Alpha-1 antitrypsin deficiencyAnswer
  3. C
    Hereditary hemochromatosis
  4. D
    Primary biliary cholangitis
  5. E
    Wilson disease

Answer

Alpha-1 antitrypsin deficiency
The correct answer accurately identifies alpha-1 antitrypsin deficiency based on its pathognomonic histologic appearance. Misfolded alpha-1 antitrypsin protein cannot be efficiently secreted from the liver, leading to its accumulation in the rough endoplasmic reticulum of periportal hepatocytes. Because the protein is a glycoprotein, it stains strongly with periodic acid-Schiff (PAS) and cannot be degraded by the enzyme diastase, rendering it diastase-resistant. This directly correlates with the patient's transaminitis and his mild exertional dyspnea (a sign of early panacinar emphysema).

Step-by-Step Solution

1
Analyze the patient's clinical presentation.
The patient is a young adult presenting with mild exertional dyspnea and unexplained transaminitis.
Identifying the affected organ systems (lungs and liver) helps narrow the differential diagnosis for systemic diseases.
2
Evaluate the specific histopathologic findings from the liver biopsy.
The biopsy shows intracytoplasmic, round, eosinophilic inclusions in periportal hepatocytes that are PAS-positive and diastase-resistant.
Special stains are critical for definitive diagnosis. A PAS-positive reaction that resists diastase digestion indicates the presence of glycoproteins, differentiating it from glycogen (which is diastase-sensitive).
3
Synthesize the clinical and pathologic data to formulate a diagnosis.
The combination of early pulmonary symptoms, hepatic involvement, and the pathognomonic biopsy finding of misfolded glycoprotein accumulation confirms alpha-1 antitrypsin deficiency.
Misfolded alpha-1 antitrypsin polymerizes and becomes trapped in the rough endoplasmic reticulum of hepatocytes, directly causing the observed staining pattern.

Key Concept

The hallmark histologic finding of hepatic involvement in alpha-1 antitrypsin (A1AT) deficiency is the presence of unsecreted, misfolded A1AT glycoproteins in the endoplasmic reticulum of periportal hepatocytes, which appear as PAS-positive, diastase-resistant intracytoplasmic inclusions.
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Topics

Pathology and Biopsy Interpretation

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