Primary biliary cholangitis (PBC) is characterised by autoimmune destruction of interlobular bile ducts. The most specific autoantibody, positive in >90% of PBC patients, targets which mitochondrial antigen?

• A Anti-mitochondrial antibody (AMA) targeting PDC-E2 (E2 subunit of pyruvate dehydrogenase complex) ✓
• B Anti-smooth muscle antibody (ASMA) targeting F-actin
• C Anti-liver-kidney-microsomal antibody (anti-LKM1) targeting CYP2D6
• D pANCA targeting myeloperoxidase in bile duct epithelium

Explanation

Anti-mitochondrial antibody (AMA) directed against the E2 subunit of the pyruvate dehydrogenase complex (PDC-E2) on the inner mitochondrial membrane is present in >90% of PBC patients and is highly specific for the diagnosis. AMA is detected by immunofluorescence showing cytoplasmic staining of kidney, stomach, and liver (Type M2 pattern). ASMA is seen in type 1 autoimmune hepatitis. Anti-LKM1 (anti-CYP2D6) characterises Type 2 autoimmune hepatitis. pANCA is associated with primary sclerosing cholangitis and ulcerative colitis.

Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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