Lupus-like syndrome induced by procainamide

Fifteen patients with a procainamide-induced lupus-like syndrome have been studied. On the basis of clinical manifestations, three groups were recognized: (1) An asymptomatic group of 4 patients; (2) a group of 5 patients with abnormalities limited to joints; and (3) a group of 6 patients demonstrating the more classic syndrome of systemic lupus. All patients had elevated serum titers of antinuclear antibodies, and 11 had positive LE cell preparations. The syndrome developed as quickly as two weeks after institution of procainamide and with as small a dosage as 0.75 gm. daily. After the drug was discontinued, clinical and serologic findings receded rapidly. It required from several days to five weeks for symptoms to disappear. In 2 patients, however, the manifestations were long-lasting even after discontinuation of procainamide. The immunologic reaction to procainamide occurs frequently. It is suggested that all patients receiving this drug have periodic blood determinations for circulating antinuclear factors.