Infliximab (Remicade ) to Treat Dermatomyositis and Polymyositis

This study will examine whether infliximab (Remicade ) is safe and effective for the treatment of dermatomyositis and polymyositis. Infliximab blocks the effect of a protein called tumor necrosis factor (TNF), which is associated with harmful inflammation in many diseases. Patients 18 years of age and older with active dermatomyositis or polymyositis that does not respond adequately to treatment with methotrexate and corticosteroids may be eligible for this study. Candidates will be screened with a medical history, physical examination, blood and urine tests, chest x-ray, pulmonary function test, skin test for tuberculosis, HIV test, electromyography (described below), manual muscle testing, and functional assessments. Magnetic resonance imaging (described below) will be done to assess the degree and location of inflammation in the involved limbs. An electrocardiogram and echocardiogram will be done if recent ones are not available. Patients who qualify for the study will be asked to undergo two muscle biopsies (surgical removal and analysis of small pieces of muscle tissue), one before initiation of treatment and another on the 16th week . Participants will be randomly assigned to receive either 3 mg/kg body weight of infliximab or a placebo (inactive substance) by infusion through a vein over 2 hours. The infusions will be given at the beginning of the treatment period (week 0) and at weeks 2, 6 and 14. At week 16, strength will be assessed by manual muscle testing. Patients who improved with treatment will continue with the same infusion dose on weeks 18, 22, 30, and 38. Those who do not improve will be assigned by random allocation to receive either 5 mg/kg body weight or 10/mg/kg body weight of infliximab on weeks 18, 22, 30 and 38. Those who did not improve who were previously on the placebo infusion will receive an extra dose of either 5 mg/kg or 10 mg/kg body weight of infliximab on week 16, while those patients who were previously on 3 mg/kg body weight o