A 34-year-old man presents with hemoptysis, chronic sinusitis, and a nodular lung lesion. Biopsy demonstrates necrotizing granulomatous vasculitis of small vessels. Serology shows cytoplasmic staining of ethanol-fixed neutrophils with a diffuse fine granular pattern. The antigen targeted by these antibodies is:

• A Myeloperoxidase
• B Double-stranded DNA
• C Glomerular basement membrane collagen IV alpha3
• D Proteinase 3 ✓

Explanation

Granulomatosis with polyangiitis (Wegener) is associated with c-ANCA, a cytoplasmic diffuse granular pattern caused by antibodies against proteinase 3 contained in neutrophil azurophilic granules. Myeloperoxidase antibodies produce a perinuclear pattern (p-ANCA) seen in microscopic polyangiitis and eosinophilic granulomatosis with polyangiitis. Anti-GBM antibodies are linear on renal biopsy, and dsDNA antibodies characterize SLE.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.