Patients with antibodies to both PmScl and dsDNA.

Objective: To determine the significance of dsDNA antibodies in patients with antibodies to PmScl.

Methods: All patients testing positive for PmScl and/or dsDNA antibodies at an academic medical center between 1977 and 2002 were identified. Charts for the PmScl-positive patients were reviewed for manifestations of lupus, scleroderma, or polymyositis/dermatomyositis. Patients with antibodies to dsDNA were matched to each of the double-positive PmScl+/dsDNA+ patients on the basis of sex, race, age, and date of autoantibody testing. Standard classification criteria for lupus, scleroderma, and myositis were used (excluding dsDNA, PmScl, or antinuclear antibodies as criteria), and the number of subjects meeting classification criteria was recorded.

Results: Records were available for 38 out of 47 patients who were identified as PmScl-positive. The prevalence of dsDNA antibodies in this group was 42% (16/38). Patients with PmScl and dsDNA antibodies had a higher prevalence of systemic lupus erythematosus (8/16 vs 2/22; p = 0.008) and a lower rate of scleroderma or myositis (1/16 vs 9/22; p = 0.025) than dsDNA-negative patients with PmScl antibodies. The prevalence of systemic lupus erythematosus, myositis, and scleroderma in patients with PmScl and dsDNA antibodies was not different from the prevalences of these diseases in a matched cohort of patients who were dsDNA-positive.

Conclusion: Antibodies to PmScl are associated with scleroderma and myositis when dsDNA antibodies are not present. In the presence of dsDNA antibodies, PmScl antibodies do not appear to have clinical relevance.