Prevalence of overlap of antineutrophil cytoplasmic antibody associated vasculitis with systemic autoimmune diseases: an unrecognized example of poliautoimmunity.

We aimed to estimate the frequency of overlap of antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) with systemic autoimmune diseases. Retrospective single-center study to identify patients with AAV diagnosis and concomitant autoimmune systemic diseases, simultaneously, before or after the diagnosis of AAV. Sociodemographic characteristics, such as comorbidities; follow-up time; type of AAV; disease duration; relapses; treatment and response; clinical, serological, and histological characteristics; disease activity and damage; prognosis; dialysis requirements, and death were assessed. Twenty-eight of two hundred and forty-seven patients (11.3%) with AAV had a concomitant diagnosis of autoimmune disease. The predominant AAV type was renal-limited vasculitis (39%), followed by granulomatosis with polyangiitis (29%), mycroscopic polyangiitis (25%), and eosinophilic granulomatosis with polyangiitis (7%). Mean age at AAV diagnosis was 50 ± 17 years and 24/28 were ANCA positive. The main clinical manifestations were renal (79%), otorhinolaryngologic (43%), and pulmonary and peripheral neuropathy (32%). Sixteen patients (57%) experienced partial or total remission at a median follow-up of 34 months, and four patients (14%) died. The most frequent autoimmune disease overlapped was rheumatoid arthritis (39%), followed by Sjögren's syndrome and systemic sclerosis (14%), mixed connective tissue disease (11%), systemic lupus erythematosus and juvenile idiopathic arthritis (7%), and ankylosing spondylitis and IgG4-related disease (4%). In nine patients (32%), both diagnoses were simultaneous; in the rest, median time elapsed between the autoimmune disease and AAV diagnosis was 173 months. The prevalence of overlap AAV with other autoimmune diseases was low. The most common AAV phenotype was renal-limited vasculitis, and the most frequent overlap disease was rheumatoid arthritis.