Tacrolimus-associated myositis: a case report in a renal transplant patient.

A 55-year-old Caucasian man who had received a second kidney graft in July 1993, was switched from cyclosporine to tacrolimus in June 2000 due to deterioration of renal function. Thereafter, he began to complain of muscle cramps in both quadriceps with an increased CPK and EMG findings of polyneuropathy. A muscle biopsy demonstrated acute myositis. Prednisone was administered with amelioration of the patient's symptoms, but with persistently increased CPK and myoglobin levels. In February 2001, mycophenolate mofetil was introduced and tacrolimus tapered to 3 mg daily to seek a toxic role of this immunosuppressant, since there was no other cause of myositis. A sudden decrease in CPK was observed, but the complete normalization took place only after its withdrawal in September 2002. This case represents a tacrolimus-associated myositis.