[Is myositis in chronic polyarthritis using d-penicillamine drug-induced?]

Myositis was diagnosed twenty months after starting treatment with d-penicillamine in a patient suffering from uncomplicated rheumatoid arthritis for nearly three years. The diagnosis was established by electromyographic investigation and by biopsy. In this patient d-penicillamine had been intermittently increased to a dose over 1 g per day and then reduced because of mild proteinuria. The appearance of myositis during d-penicillamine therapy, its immediate regression on discontinuing the drug, and the absence of signs of vasculitis or other extraarticular manifestations in this patient suggest that this complication may be drug-induced. The clinical course is compared with isolated cases reported in the literature. The significance of this rare side effect is discussed.