Microscopic polyangiitis and polyarteritis nodosa: How and when do they start?

Objective. To describe initial clinical symptoms attributable to microscopic polyangiitis (MPA) or polyarteritis nodosa (PAN). Methods. We retrospectively reviewed the medical files of 72 patients (mean followup 6.7 years) with biopsy-proven MPA (n = 36) or PAN (n = 36). Results. Initial manifestations were similar in both entities except for peripheral neuropathy (P = 0.02) and gastrointestinal tract involvement (P = 0.006), which were significantly more frequent in PAN, and general signs alone in MPA (8%; P = 0.02). The mean time to diagnosis was 9.8 +/- 19.4 months; 35% of the patients died and 26% relapsed; significantly more MPA than PAN patients relapsed (P = 0.03). Time to diagnosis greater than or equal to90 days was associated with a trend toward more patients relapsing (P = 40.12), but not with an increased risk of mortality. Conclusion. Initial symptoms of MPA and PAN are usually nonspecific and last for several months before the diagnosis is made. A longer time to diagnosis is associated with a tendency to a higher relapse rate.