Fibromyalgia syndrome and disease activity in systemic lupus erythematosus

To study the effect of fibromyalgia syndrome (FS) on the expression of systemic lupus erythematosus (SLE) and on the measurement of disease activity, we performed a cross-sectional study of subjects with SLE. Eighty-seven subjects were studied and 22 (25.3%), all female, had FS (Yunus' criteria). Disease activity and organ system involvement were assessed using the systemic lupus activity measure (SLAM) and using 10 cm visual analogue scales (VAS) completed by both physician and patient. No significant difference between FS and non-FS groups in the objective measurement of disease activity was present, median (range) SLAM scores being 5 (0-18) and 6 (0-24), respectively (NS). Similarly, expression of SLE, as measured by the prevalence of specific organ system involvement, was similar in the two groups. In contrast the prevalence of glucocorticoid use, antibodies to DSDNA and fulfilling four ACR criteria was higher in the non-FS group. The rating of SLE disease activity was affected by concomitant FS. Physician and patient disease activity VAS correlated significantly with SLAM scores in non-FS subjects (P < 0.001, Spearman analysis), whereas in FS subjects, neither physician nor patient VAS correlated with SLAM scores. We conclude that FS is prevalent in individuals with SLE and does not affect disease expression but may interfere with the rating of disease activity.