Does searching for antineutrophil cytoplasmic antibodies help with the diagnosis of Adult-onset Still's disease?

Adult-onset Still's disease (AOSD) is a rare systemic inflammatory disorder of unknown etiology. It is a seronegative disease with multisystemic manifestations. One of the important laboratory findings in AOSD is negative results for rheumatoid factor and antinuclear antibody. Because there is no specific, pathognomonic test for AOSD, diagnosis is based on a set of clinical and laboratory criteria and exclusion of other diseases like infections, malignancies, and vasculitis. It is obvious that antineutrophil cytoplasmic antibodies (ANCAs) are specific for vasculitis; however, few studies detected some types of these antibodies in rheumatoid arthritis, juvenile chronic arthritis, and still's disease. The aim of this study was to investigate whether or not ANCAs exist in sera of patients with AOSD. Forty-one AOSD patients were enrolled in this prospective study; patients were diagnosed according to Yamaguchi criteria and exclusion of other diseases by at least 6-months follow-up. Sera from all patients were tested for p-ANCA and c-ANCA by indirect immunofluorescence assay. Confirmatory antigenic testing for proteinase 3 (PR3) and myeloperoxidase (MPO) ANCA subtypes then were performed on positive sera. Only one patient with AOSD in this study showed low titer of MPO-ANCA in her sera. In a 1-year follow-up, ANCA did not predict vasculitis in this patient. This study suggested that patients with AOSD are mostly seronegative for ANCAs too. Positive ANCA appears to be an epiphenomenon and has not any association with vasculitis in AOSD.