Direct immunofluorescence of normal skin in rheumatoid arthritis

The clinical significance of previously described immunoglobulin and complement deposition in the superficial dermal vessel walls of patients with rheumatoid arthritis is unknown. In the present study, skin biopsies were obtained from the normal forearm and buttock of 48 unselected patients with rheumatoid arthritis and were examined by direct immunofluorescence (IF) for the presence of immunoglobulin (IgG,A,M) and complement (C3) in the vessel walls. Deposits of C3, IgM or IgG were detected in 10 patients. Five patients had deposits at the forearm sample alone, four patients had deposits at both biopsy sites, while one patient was positive at the buttock alone. Clinical features were similar in patients with and without vessel IF. However, patients with IF were significantly more seropositive with lower levels of complement and raised levels of serum IgA and IgM. There was also an increased level of circulating IgG immune complexes in these patients. Further analysis following exclusion of seronegative patients revealed similar results. This study suggests that the presence of vessel IF identifies a subgroup of patients who have evidence of more severe immunological disturbance.