A 28-year-old man presents with hemoptysis, chronic sinusitis, and nodular lung lesions. Biopsy of lung tissue shows necrotizing granulomatous vasculitis. Cytoplasmic staining pattern on ethanol-fixed neutrophil indirect immunofluorescence is positive. The target antigen of these autoantibodies is:
- A Myeloperoxidase
- B Proteinase 3 ✓
- C Glomerular basement membrane type IV collagen alpha-3 chain
- D Double-stranded DNA
Correct answer: B. Proteinase 3
Explanation
Granulomatosis with polyangiitis (Wegener granulomatosis) is strongly associated with c-ANCA, directed against proteinase 3, giving a diffuse cytoplasmic staining pattern on ethanol-fixed neutrophils. Myeloperoxidase antibodies produce a perinuclear pattern (p-ANCA) and are typical of microscopic polyangiitis and eosinophilic granulomatosis with polyangiitis. Anti-GBM antibodies against the alpha-3 chain of type IV collagen define Goodpasture syndrome, which lacks granulomas and ANCA positivity.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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