Raised serum S100B protein levels in neuropsychiatric lupus

Objective: To test serum S100B protein levels in patients with and without neuropsychiatric systemic lupus erythematosus (NPSLE) and controls. Methods: 87 patients with SLE, 23 with and 64 without neuropsychiatric involvement, and 25 control subjects were prospectively evaluated. NPSLE diagnosis was made according to the American College of Rheumatology nomenclature and case definitions for neuropsychiatric lupus syndromes. Serum S100B protein levels were determined with a luminescence immunoassay. Statistical analysis was performed using Mann-Whitney and Kruskal-Wallis tests. Results: Among the patients with NPSLE, 9 presented psychosis; 4, cranial neuropathy; 3, cerebrovascular disease; 1, seizures; 1, chorea; 1, peripheral polyneuropathy; 1, multiplex mononeuropathy; 3, dementia. Serum concentrations of S100B protein were significantly higher in patients with NPSLE (median 0.164 ng/ml, interquartile range 0.113-0.332) than in non-NPSLE patients (0.062 ng/ml, 0.026-0.109) and controls (0.088 ng/ml, 0.013-0.124) (p < 0.001). Patients with anti-dsDNA antibodies had higher S100B protein levels (p = 0.001). No significant associations were found of lupus activity (among non-NPSLE cases), antiphospholipid antibodies, and reduced complement levels with S100B concentration. Conclusions: Serum S100B protein level is raised in NPSLE, reflecting continuing neurological damage. The association of anti-dsDNA antibodies with higher S100B protein concentration deserves further study.