Inflammatory myopathy with abundant macrophages

A rare idiopathic inflammatory myopathy characterized by diffuse destructive infiltration of CD68+ macrophages into the fascia rather than muscle fibers in muscle biopsies, proximal muscle weakness and myalgia with or without scaly dermatomyositis-like or atypical non-dermatomyositis-like skin lesions, elevation of creatine kinase levels and thickening of muscle fascia in muscle MRI.