Dx studies of Granulomatosis with polyangiitis

90% ⊕ ANCA (80% PR3, 20% MPO), less Se in limited upper-airway disease

CXR or CT → nodules, infiltrates, cavities; sinus CT → sinusitis ± bone erosions ↑ BUN & Cr, proteinuria, hematuria; sediment w/ RBC casts, dysmorphic RBCs Biopsy → necrotizing granulomatous inflammation of arterioles, capillaries, veins. Renal bx w/ pauci-immune (minimal immune deposition) necrotizing and crescentic GN.