Infantile polymyositis: A case report

A 10-month-old Japanese boy developed progressive muscle weakness and hypotonia at 3 months of age. Because of striking inflammatory cellular infiltration in his muscle biopsy, he was diagnosed as having infantile polymyositis and was placed on steroid and immunosuppressive medication when he was 10-month-old. His physical condition was not significantly altered, though serum creatine kinase (CK) level was normalized (1,500 iu/l → 90 iu/l). These findings contrast with previous reports documenting improvement with steroid administration.