Backdround Anti-Smith (Sm) antibodies are highly specific for systemic lupus erythematosus (SLE), their associations with some organ involvements were described.

Objectives The aim of our study was to determine clinical, biological and immunological characteristics in SLE patients according to the presence of anti-Sm antibodies.

Methods A retrospective study of a group of Tunisian patients with SLE (fulfilling the ACR revised criteria) was conducted in an internal medicine department. Patients were divided in two groups according to the presence (groupe1) or not (group 2) of anti-Sm antibodies. Variables with a p inferior to 0.05 were considered to be statistically significant.

Results Anti-Sm antibodies were screened in 153 among 246 SLE patients and were positive in 64% of patients. Mean age at SLE diagnosis was significantly lower in the group 1 (31.82 years±12.70 vs 36.16 years±12.34; p=0.043). Poor general state was the only clinical feature significantly more frequent in group 1 (54.2% vs 36.5%; p=0.04). Lupus nephritis was more frequent in patients with anti-Sm antibodies without significant difference (47.9% vs 38.2%; p=0.24). Arthritis were more frequent in group 2 (42.6% vs 50%; p=0.38). Central nervous system manifestations (16.7% vs 16.4%), pericarditis (36.1% vs 31.4%) and pleural effusion (23.4% vs 27.8%) were similar in the two groups. Anaemia (77.1% vs 74.5; p=0.7), leucopenia (49% vs 47.2%; p=0.8) and thrombocytopenia (26% vs 15%; p=0.12) were more frequent in patients with anti-Sm antidodies without significant differences. Anti-Sm antibodies were significantly associated with anti-RNP antibodies (78.6% vs 17.6%; p<0.0001). Remission was less frequent is group 1 (70.4% vs 82.9%; p=0.14) and death was more frequent in this group (16% vs 10.3%; p=0.4) without significant differences.

Conclusions In our patients, anti-Sm antibodies prevalence was higher than those reported in other cohorts (5% to 49%). Patients with anti- Sm antibodies seem to develop clinical SLE manifestations earlier than other patients. In our study, anti-Sm antibodies doesn’t influence SLE clinical course and weren’t associated with hematologic disorders, whereas in another series, anti-Sm antibodies were associated with lupus nephritis, serositis, anaemia and leucopenia.