Microscopic polyangiitis: Clinical and laboratory findings in eighty‐five patients

Objective To retrospectively analyze the clinical symptoms, laboratory findings, and outcomes in patients with microscopic polyangiitis (MPA) who were enrolled in various clinical trials conducted by the French Vasculitis Study Group. Methods A cohort of 85 patients meeting the Chapel Hill criteria for MPA participated in the study. Seventy‐one of them were included in prospective therapeutic trials. Eighty‐one diagnoses were biopsy proven. In the other patients, diagnosis was based on clinical findings. Results Forty‐seven men and 38 women, with a mean ± SD age of 56.8 ± 14.6 years, met the criteria for MPA. Their main clinical symptoms were renal manifestations (78.8%), weight loss (72.9%), skin involvement (62.4%), fever (55.3%), mononeuritis multiplex (57.6%), arthralgias (50.6%), myalgias (48.2%), hypertension (34.1%), lung involvement (24.7%; alveolar hemorrhage 11.8%), and cardiac failure (17.6%). The mean ± SD serum creatinine level before treatment was 2.59 ± 2.96 mg/dl; 47 patients had renal insufficiency (serum creatinine >1.36 mg/dl). Eight patients underwent dialysis at the time of diagnosis, and long‐term dialysis was necessary for 10 patients. Antineutrophil cytoplasmic antibodies (ANCA) were present in 38 of 51 patients (74.5%), of whom 33 had a perinuclear staining pattern (pANCA) and 5 had a cytoplasmic pattern. Antibodies to proteinase 3 were present in 4 patients and antibodies to myeloperoxidase were detected in 31, as determined by enzyme‐linked immunosorbent assay. Of the 30 patients who underwent renal and celiac angiography, 4 had microaneurysms. Of the 29 patients (34.1%) who had relapses, 8 died during or after the relapse. During followup, 28 of the 85 patients (32.9%) died. The mean ± SD duration of followup of the group was 69.9 ± 60.6 months. Deaths were less frequent when patients had been treated with steroids and immunosuppressive drugs (13 patients [24.1%]) than with steroids alone (15 patients [48.4%]) ( P < 0.01). The 5‐year survival rate was 74%. Conclusion This study demonstrated that MPA is a multisystemic disease in which renal symptoms are frequent, but the disease is also associated with general symptoms, arthritis, mononeuritis multiplex, and other manifestations that are also seen in various vasculitides. The rarity of abnormal angiogram findings and the high frequency of pANCA are characteristic of MPA. In most cases, the outcome is comparable with those of other systemic vasculitides, but relapses are frequent.