A 40-year-old woman is found to have primary biliary cholangitis (PBC). Liver biopsy shows florid duct lesion — granulomatous destruction of medium-sized bile ducts with lymphocytic and plasma cell infiltration. Which antibody is the MOST specific serological marker?
- A Anti-mitochondrial antibody (AMA) targeting pyruvate dehydrogenase complex E2 subunit ✓
- B Anti-smooth muscle antibody (ASMA) — marker of autoimmune hepatitis
- C Anti-LKM1 antibody (anti-liver kidney microsomal type 1) — AIH type 2
- D pANCA — primary sclerosing cholangitis and AIH overlap
Correct answer: A. Anti-mitochondrial antibody (AMA) targeting pyruvate dehydrogenase complex E2 subunit
Explanation
Anti-mitochondrial antibody (AMA), particularly the M2 subtype targeting the E2 subunit of the pyruvate dehydrogenase complex (PDC-E2) on the inner mitochondrial membrane, is present in >95% of PBC patients and is highly specific. PBC is an autoimmune cholestatic liver disease predominantly affecting middle-aged women, with destruction of small intrahepatic bile ducts leading to cholestasis, portal hypertension, and eventually cirrhosis. ASMA is for AIH type 1; anti-LKM1 for AIH type 2; pANCA for PSC.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.