A pediatric case of polymyositis associated with Mycoplasma pneumoniae infection.

We describe the case of a 10-year-old girl who developed polymyositis associated with a Mycoplasma pneumoniae infection. She exhibited mild muscle weakness without skin rash, markedly elevated serum levels of muscle enzymes, and infiltration of mononuclear cells in a muscle biopsy specimen. Efficacy of both oral prednisolone and of intravenous methylprednisolone pulse therapy for her disease was limited. However, other immunosuppressive drugs, cyclophosphamide and methotrexate, proved clinically effective. This is the first report of steroid-resistant polymyositis associated with M. pneumoniae infection in a child.