Antibodies to Sm in patients with systemic lupus erythematosus. Correlation of Sm antibody titers with disease activity and other laboratory parameters.

Thirty patients with systemic lupus erythematosus (SLE) were studied over a 2.5-year period. The group was divided into 14 patients with antibodies to Sm and a control group that failed to exhibit antibodies to Sm over the study period. The titer of antibodies to Sm fluctuated in all 14. A rising titer of antibodies to Sm 1) predicted a flare disease in 50% an 2) correlated with an exacerbation of disease in 60%. Patients with antibodies to Sm had a comparable incidence of severe disease, renal disease, and central nervous system disease. They exhibited significantly more leukopenia and antibodies to non-Sm, non-RNP extractable nuclear antigen. In only 1 patient, a rise in titer of antibodies to Sm did not correlate with or predict a disease flare in contradistinction to other serologic markers of SLE, specifically antibodies to double-stranded DNA and cryoglobulins. Though infrequently detected, antibodies to Sm can help in the management of patients with SLE.