Antineutrophil cytoplasmic antibodies in inflammatory arthritis--potential for misdiagnosis?

Antineutrophil cytoplasmic antibodies (ANCA) are well described in Wegener's granulomatosis and some forms of vasculitis. They have also been described in patients with arthritis, but the specificity of these ANCA and their relationship to the presence of vasculitis, antinuclear antibodies (ANA) and granulocyte-specific ANA (GS-ANA), and to disease activity are uncertain. We studied 101 patients with forms of inflammatory arthritis and detected four cytoplasmic ANCA, eight perinuclear ANCA and 16 atypical ANCA. There was no association between the presence of ANCA and ANA or rheumatoid factor. No anti-PR3 antibodies were found and no strong anti-myeloperoxidase antibodies were detected. Four GS-ANA were detected and were distinct from ANCA. There was no association between rheumatoid arthritis disease activity or disability and ANCA status. ANCA did not predict vasculitis over a 3 yr follow-up. These ANCA appear to be epiphenomena. Their importance lies in their potential to mislead physicians towards a misdiagnosis of vasculitis.