Efficacy of tacrolimus in treatment of polymyositis associated with myasthenia gravis.

We report a patient with polymyositis (PM) associated with myasthenia gravis (MG). Both disorders had been controlled for around 15 years by oral prednisolone and a cholinesterase inhibitor following surgical removal of invasive thymoma and radiotherapy, but muscular weakness due to myalgia and an increase in serum levels of myogenic enzymes, mainly ascribable to the recurrence of PM, reappeared immediately after cessation of these drugs, which was done because the patient had multiple bone fractures and severe osteoporosis due to the long-term corticosteroid therapy. Oral tacrolimus was therefore tried, and produced an improvement in muscular symptoms in association with normalization of myogenic enzymes. PM associated with MG as in this patient might be the best indication for tacrolimus, considering its efficacy in MG, but this drug should also be actively considered as a therapeutic option in refractory cases of PM alone, particularly when either corticosteroids or other immunosuppressive agents are not usable.