Autoantibodies to myeloperoxidase in systemic sclerosis.

OBJECTIVE

Although antimyeloperoxidase (MPO) antibodies provide a sensitive serological test for vasculitis, their significance in sera from a small proportion (about 10%) of patients with autoimmune rheumatic disease is controversial. Our aim was to determine the incidence of anti-MPO antibodies in sera from patients with systemic sclerosis (SSc) and their relation to renal disease.

METHODS

Thirty-eight patients had limited cutaneous SSc (lSSc) and 43 diffuse cutaneous SSc, and within each group, 24 and 27 patients, respectively, had renal impairment (defined as stable creatinine clearance less than 60 ml/min). Six patients previously had had a scleroderma renal crisis. After screening for antineutrophil cytoplasmic antibodies (ANCA) by indirect immunofluorescence, the levels of IgM and IgG anti-MPO antibodies in 8 patients with SSc was determined by ELISA, with human MPO as antigen.

RESULTS

Sera from 2 patients, both with lSSc and renal impairment, were perinuclear p-ANCA positive and had significant levels of circulating IgM and IgG anti-MPO antibodies. In one patient, anti-MPO antibodies appeared in the serum only after D-penicillamine was introduced, continued to rise after withdrawal of the drug, and fell only after immunosuppressive therapy. Renal biopsy confirmed vasculitis. The 2nd patient died of unrelated disease before further investigations could be performed.

CONCLUSION

We suggest that circulating anti-MPO antibodies are not a feature of SSc per se and, if found, may indicate the presence of an unrelated pathology, such as idiopathic or drug induced vasculitis.