Serum IgA and gold-induced toxic effects in patients with rheumatoid arthritis.

Serum Immunoglobulin concentrations were measured prospectively in 25 patients with rheumatoid arthritis at months 0, 1, 3, 6, and 12 of aurothloglucose treatment. Substantial lowering of IgA and IgM levels was found at month 3 and thereafter, and of IgG at month 12 only. When patients in whom drug-induced toxic effects developed at any time during treatment (toxic group) were compared with those who did not (nontoxic group), serum levels of IgA and to a lesser degree of IgG, but not of IgM, were found to be substantially lower in the toxic than in the nontoxic group, both at the onset and during treatment, except for IgG at month 12. When measured at the moment of toxic effect, only igA, but not IgG and IgM, was substantially lower than in serum samples of patients without toxic effects at that moment. The serum IgA concentration in patients with rheumatoid arthritis seems to be related to whether or not aurothioglucose-induced toxic effects occur.