PR3-ANCA positivity is most characteristic of Wegener's granulomatosis. Which disease does this indicate?

• A. Wegener's granulomatosis
• B. Churg-Strauss syndrome
• C. Goodpasture syndrome
• D. Henoch-Schonlein purpura

Answer: (A)

PR3-ANCA, also known as c-ANCA, is classically linked to granulomatosis with polyangiitis (the condition historically called Wegener's granulomatosis). The presence of this antibody points toward GPA because it targets proteinase 3 in neutrophils and is strongly associated with the necrotizing granulomatous inflammation of the respiratory tract plus pauci-immune glomerulonephritis that defines GPA.

Churg-Strauss (eosinophilic granulomatosis with polyangiitis) can be ANCA-associated but more often shows MPO-ANCA with prominent eosinophilia. Goodpasture syndrome involves anti-GBM antibodies, not ANCA. Henoch-Schönlein purpura is an IgA immune complex vasculitis, not driven by ANCA.

So, PR3-ANCA positivity most strongly indicates Wegener's granulomatosis (granulomatosis with polyangiitis).