Cutaneous immunofluorescence in ankylosing spondylitis. Absence of correlation with disease activity.

Biopsy specimens of normal skin from 43 patients with ankylosing spondylitis (AS) were studied for immunoglobulin and complement deposition by immunofluorescence and for histological abnormalities by light microscopy. The results were compared with those of 17 healthy subjects. Perivascular deposits of IgA, IgG, IgM and C3 were found in 26, 47, 56 and 33%, respectively, of the patients with AS. Skin deposits of IgA, IgG and C3 occurred significantly more frequently in patients with AS compared to healthy subjects. Perivascular mononuclear cell infiltration was found in only 8 (19%) of the patients with AS. The results of both immunofluorescence and histologic studies did not correlate with disease duration, disease activity, extraarticular features or the presence of circulating immune complexes. Our findings suggest a role of humoral immunopathological mechanisms in AS but also show that cutaneous immunofluorescence cannot serve as a marker of disease activity.