A 52-year-old woman presents with rapidly progressive glomerulonephritis, hemoptysis, palpable purpura, and mononeuritis multiplex. Indirect immunofluorescence shows a perinuclear staining pattern of ethanol-fixed neutrophils, and ELISA confirms antibodies to myeloperoxidase. Renal biopsy shows necrotizing crescentic glomerulonephritis with few or no immune deposits. The most likely diagnosis is:

• A Granulomatosis with polyangiitis
• B Goodpasture syndrome
• C Polyarteritis nodosa
• D Microscopic polyangiitis ✓

Explanation

Perinuclear ANCA with antimyeloperoxidase specificity defines the pauci-immune small-vessel vasculitides, and microscopic polyangiitis is the prototypical MPO-positive entity combining necrotizing crescentic GN with pulmonary capillaritis. Granulomatosis with polyangiitis is associated instead with cytoplasmic ANCA against proteinase 3 and features necrotizing granulomas of the upper airway. Polyarteritis nodosa is ANCA negative and involves medium-sized vessels without glomerular crescents, and Goodpasture syndrome shows linear IgG deposition along the GBM.

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.