A 34-year-old woman presents with three weeks of malaise, arthralgia, hematuria and rising creatinine. Urinalysis shows dysmorphic red cells and red cell casts. Renal biopsy reveals segmental fibrinoid necrosis and cellular crescents with essentially no immunoglobulin or complement staining. Serology shows perinuclear ANCA with specificity for myeloperoxidase. The most likely diagnosis is:

• A Post-infectious glomerulonephritis
• B Lupus nephritis class III
• C Microscopic polyangiitis with pauci-immune crescentic glomerulonephritis ✓
• D IgA nephropathy with crescents

Explanation

Pauci-immune necrotizing crescentic GN with MPO-ANCA (p-ANCA pattern) defines antineutrophil cytoplasmic antibody associated vasculitis, most commonly microscopic polyangiitis, which affects women slightly more often and may involve lungs as capillaritis. Lupus class III and post-infectious GN show granular immune deposits on immunofluorescence, and IgA nephropathy shows dominant mesangial IgA, all excluding them here.

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.