Expression profiling of human myositis muscle samples This study was designed to compare expression signatures among the various types of inflammatory myopathy, dermatomyositis (DM), inclusion body myositis (IBM), necrotizing myopathy (NM), nonspecific myopathy (NS), and polymyositis (PM) compared to normal (NL) muscle. Overall design: Muscle samples from human biopsies with DM, IBM, NM, NS, PM, or normal were studied for gene expression to identify differentially expressed genes.