Immunoglobulin deficiency in patients with systemic lupus erythematosus.

Hypergammaglobulinemia is a common laboratory finding in patients with active systemic lupus erythematosus; in contrast, immunoglobulin deficiency, except for immunoglobulin A, is unusual. We report 18 patients who developed low immunoglobulin G levels 4 months to 22 years (median = 4 years) following the diagnosis of systemic lupus erythematosus. This phenomenon was transient in 10 patients (median duration 10.5 months). Eight patients had received cytotoxic drugs prior to the development of hypogammaglobulinemia, while all had received prednisone. The nadir levels of serum IgG were 132-550 mg/dl (median = 363 mg/dl). The presence and degree of immunoglobulin G deficiency did not correlate, in general, with the type or dose of medication. None of the patients had renal failure. Only 4 patients developed recurrent infections. Urinary loss of protein was not a cause of this disorder. Study of the in vitro cellular immune responses of peripheral blood lymphocytes in 5 patients showed that excessive 'suppressor' T cell activity and decreased numbers of B cells may be responsible for the development of immunoglobulin deficiency. Serum immunoglobulin levels should not be employed as an indication of disease activity in systemic lupus erythematosus, as all 18 patients continued to have significant clinical disease. Deficiencies of immunoglobulins are often transient and may not require treatment.