Rheumatoid factor in patients with systemic lupus erythematosus.

One hundred sixty-six patients with systemic lupus erythematosus (SLE) were surveyed and their sera tested for the presence of rheumatoid factor (RF). Fifteen were positive whenever tested, with titers of at least 1:40; the remainder were either positive only in titers of 1:20, were inconsistently positive or were persistently negative. The former group were less likely to have severe manifestations of SLE, less likely to have required treatment with "high-dose" steroids or a cytotoxic drug, and less likely to have had an episode of herpes zoster. We conclude that in patients with SLE, RF may be a reflection of relative immune competence so that they are partially protected against the more serious manifestations of SLE and the development of herpes zoster.