The simultaneous expression of 10,000 genes was measured, using Affymetrix GeneChip microarrays, in muscle specimens from 45 patients with various myopathies (dystrophy, congenital myopathy, and inflammatory myopathy) examined at Brigham and Women’s Hospital, and Children’s Hospital, Harvard Medical School, Boston, MA. Bioinformatics techniques were also used to classify specimens from 14 patients with subtypes of inflammatory myopathy (IM) - dermatomyositis, polymyositis, and inclusion body myositis (IBM) - and to identify the gene profiles. Ten of 11 patients with IM, and 10 of 12 with Duchenne MD were correctly classified. The various subtypes of IM have distinct gene expression signatures. 
COMMENT. Standard clinical and histopathological methods of differentiation of various inflammatory myopathies (IM) are not always conclusive, and misclassification may result in inappropriate management. The advent of molecular profiling techniques should provide a more accurate classification of the various subtypes of IM and other muscle diseases. An editorial comment points out that microarray analysis, while generating useful information, has methodological challenges that must be addressed before it realizes its potential in clinical research and practice.