Our patient was a 47-year-old man with ILD-PM/DM in the context of dyspnea associated with severe weakness. Creatine kinase value was increased to 1,110 units/L, and antinuclear autoantibodies were positive without anti-Jo-1. The results of an electromyogram suggested a myopathy, and the results of a deltoid biopsy confirmed the diagnosis of polymyositis. Chest radiograph and CT scans revealed consolidation, with air bronchograms and ground-glass opacities in both lungs with nodular opacities. Total lung capacity (TLC) was 52% of predicted values, and vital capacity (VC) was 55%. Diffusion capacity of the lung for carbon monoxide (Dlco) was 61%. The results of BAL revealed mixed alveolitis with 22% lymphocytes and 10% neutrophils. Transbronchial biopsies were not performed because of poor tolerance for BAL. Prednisone was given at 80 mg/d (1 mg/kg) with little response in terms of muscle weakness and no respiratory improvement after 15 days. A bolus of 0.6 mg/m2 of cyclophosphamide was administered, as currently recommended for refractory cases.2-4 Reassessment before the second scheduled cyclophosphamide infusion revealed a dramatic deterioration of pulmonary function (TLC, 41%; VC, 51%; and Dlco, 32%). Cyclophosphamide treatment was stopped, and IV Ig at a dosage of 2 mg/kg was begun.