In granulomatosis with polyangiitis (GPA, formerly Wegener's), the ANCA pattern on indirect immunofluorescence and the target antigen are:
- A cANCA; proteinase-3 (PR3) ✓
- B pANCA; myeloperoxidase (MPO)
- C pANCA; proteinase-3 (PR3)
- D cANCA; myeloperoxidase (MPO)
Correct answer: A. cANCA; proteinase-3 (PR3)
Explanation
GPA characteristically produces cytoplasmic ANCA (cANCA) on immunofluorescence, with the target antigen being proteinase-3 (PR3) on ELISA. Microscopic polyangiitis and eosinophilic GPA more commonly produce perinuclear ANCA (pANCA) directed against myeloperoxidase (MPO). The cANCA/PR3 pattern has ~90% specificity for active GPA in the appropriate clinical context (sinusitis, pulmonary infiltrates, glomerulonephritis).
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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