Clinical consequence and significance of anti-neutrophil cytoplasmic antibody positivity in anti-glomerular basement membrane disease

Introduction: Patients with renopulmonary syndrome who have both anti-neutrophil cytoplasmic and anti-glomerular basement membrane antibodies have been described since 1989. Aim: The aim of the authors was to analyse the data of "double positive" patients diagnosed in their department, and compare these with previous studies. Method: During the last 16 years, 87 anti-neutrophil cytoplasmic antibody positive and 11 anti-glomerular basement membrane antobody positive patients were diagnosed. Four patients with anti-glomerular basement membrane antibodies (36%) had detectable anti-neutrophil cytoplasmic antibodies, 2 patients were positive for anti-myeloperoxidase and 2 patients for anti-proteinase 3. Results: In comparison with patients having anti-glomerular basement membrane antibodies, the double-positive patients were characterized by older age (median of 46 vs. 24 years), lack of male dominance (50% vs. 71%), more frequent presence of previous extrarenal symptoms (50% vs. 0%), and lower antiglomerular basement membrane antibody levels (<100EU/ml: 100% vs. 29%). The double-positive patients had more favourable 1-year survival (100% vs. 71%), despite their older age and similar treatment regimen (immunosuppression 100% in both groups, plasmapheresis in 75% vs. 86%), but 1-year renal survival was not different (25% vs. 14%). Conclusions: In agreement with literature data, about one third of patients with anti-glomerular basement membrane antibodies had detectable anti-neutrophil cytoplasmic antibodies, and the coexistence of the two antibodies may have clinical consequences.