Clinical significance of anti-Sm antibody in systemic lupus erythematosus & related disorders.

ABSTRACT

A retrospective analysis was undertaken of the clinical and immunological profile of 33 anti-Sm antibody positive (group I) and 243 anti-Sm antibody negative (group II) patients with systemic connective tissue diseases including systemic lupus erythematosus and related disorders (overlap, mixed and undifferentiated connective tissue diseases). The disease patterns were comparable, except for cutaneous vasculitis and hypocomplementaemia (low serum C3 levels). Vasculitis was observed in 55 per cent of group I and 35 per cent of group II subjects (P less than 0.05). Hypocomplementemia was also detected more frequently (86%) in group I as compared to group II (66%) patients (P less than 0.05). No association was found between anti-Sm antibody and renal, neuropsychiatric and cardiopulmonary features. The study thus demonstrated the association of anti-Sm antibody with immune complex mediated vasculitis.