Clinical significance of anti-Sm antibodies in systemic lupus erythematosus.

Case records of 34 patients with systemic lupus erythematosus (SLE) were analyzed. Twelve patients had both anti-DNA and anti-Sm antibodies (Group I) and 22 had anti-DNA antibodies only (Group II). The disease patterns were comparable, except for (1) cutaneous vasculitis, which was observed in six of 12 patients in Group I and one of 22 in Group II (p less than 0.01); (2) pulmonary manifestations, nine of 12 in Group I and two of 22 in Group II (p less than 0.001); (3) cardiac manifestations, eight of 12 in Group I and four of 22 in Group II (p less than 0.01); and (4) renal biopsy, which showed milder lesions in Group I than in Group II (p less than 0.05). Evolution was fatal in four patients in Group I and in none in Group II. It is suggested that in SLE, the presence of anti-Sm antibody is associated with a much higher incidence of vasculitis, resulting in peculiar visceral manifestations, which can be poorly responsive to therapy. Whether there is a direct association between anti-Sm antibody and vasculitis or whether the common denominator is a genetic selection remains to be determined.