Disease spectrum of patients with antineutrophil cytoplasmic autoantibodies of defined specificity: distinct differences between patients with anti‐proteinase 3 and anti‐myeloperoxidase autoantibodies

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Abstract
Franssen C, Gans R, Kallenberg C, Hageluken C, Hoorntje S (University Hospital, Groningen; Free University Hospital, Amsterdam; and Catharina Hospital, Eindhoven; the Netherlands). Disease spectrum of patients with antineutrophil cytoplasmic autoantibodies of defined specificity: distinct differences between patients with antiproteinase 3 and antimyeloperoxidase autoantibodies. J Intern Med 1998; 244: 209–16.Objective: To compare the disease spectrum of consecutive patients with antineutrophil cytoplasmic autoantibodies directed against proteinase 3 (anti‐PR3) or myeloperoxidase (anti‐MPO).Design: Retrospective analysis.Setting: Three teaching hospitals in the Netherlands.Main outcome measures: Clinical features at presentation, histopathological characteristics and outcome.Subjects: All consecutive patients who tested positive for anti‐PR3 (n= 46) or anti‐MPO (n= 46) over an 8‐year‐period.Results: At diagnosis, patients with anti‐PR3 had a higher vasculitis activity index than patients with anti‐MPO (P < 0.001). The mean (SD) number of affected organs in the anti‐PR3 group exceeded that of the anti‐MPO group (3.9 (1.4) and 2.2 (1.1), respectively; P < 0.01). The combination of renal and respiratory tract involvement was present in as many as 78.3% of patients with anti‐PR3 and in only 23.9% of patients with anti‐MPO (P < 0.01). Renal‐limited disease exclusively occurred in patients with anti‐MPO. Granulomas were found in 41.3% of anti‐PR3‐ but in only 4.3% of anti‐MPO‐positive patients (P < 0.01). All anti‐PR3‐positive patients had Wegener's granulomatosis or microscopic polyangiitis. By contrast, diagnoses in the anti‐MPO group were more diverse: idiopathic necrotizing crescentic glomerulonephritis (26.1%), microscopic polyangiitis (26.1%), Churg–Strauss syndrome (4.3%), Wegener's granulomatosis (2.2%), giant cell arteritis (2.2%), clinically suspected vasculitis (19.6%), as well as miscellaneous nonvasculitic disorders (19.6%). During follow‐up, 10 anti‐PR3‐positive patients had 11 relapses whereas only 3 patients with anti‐MPO relapsed (P= 0.04).Conclusion: A large divergence was seen in the disease spectrum between patients with anti‐PR3 and those with anti‐MPO. In particular, extra‐renal disease manifestations, granuloma formation and relapses were more prominent in anti‐PR3‐ than in anti‐MPO‐positive patients.