A 45-year-old woman with primary biliary cholangitis (PBC) has elevated ALP, anti-mitochondrial antibodies (AMA-M2), and liver biopsy showing lymphocytic cholangitis with granulomatous destruction of small bile ducts. The specific mitochondrial antigen targeted by AMA-M2 is:
- A Pyruvate dehydrogenase complex E2 subunit (PDC-E2) ✓
- B Branched-chain 2-oxo acid dehydrogenase complex
- C Smooth muscle actin
- D Liver-kidney microsomal antigen (LKM-1)
Correct answer: A. Pyruvate dehydrogenase complex E2 subunit (PDC-E2)
Explanation
Anti-mitochondrial antibodies in PBC are directed against the E2 subunits of 2-oxo acid dehydrogenase complexes, with PDC-E2 (pyruvate dehydrogenase complex E2/dihydrolipoamide acetyltransferase) being the dominant and most specific target. AMA-M2 antibodies against PDC-E2 are present in >95% of PBC patients with high specificity. LKM-1 is the hallmark antibody in autoimmune hepatitis type 2. Smooth muscle antibodies (SMA) are found in autoimmune hepatitis type 1.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.