Clarifying the boundaries between the inflammatory and dystrophic myopathies: insights from molecular diagnostics and microarrays.

Clinical and histopathologic overlaps between the muscular dystrophies and inflammatory myopathies are being increasingly recognized. Most patients with a muscular dystrophy show improvement with prednisone treatment, although they will not be cured; many patients with idiopathic inflammatory myopathies are cured. Dysferlin-deficiency was recently recognized as a cause of late-onset dystrophy with substantial inflammation in muscle. Corticosteroid usage by these patients may result in nonrecoverable loss of strength. Therefore, it is important to rule out dysferlin-deficiency before initiating a course of corticosteroids. Newly emerging, genome-wide transcriptional profiling technology allows the identification of the interacting pathways that are active in the muscle of patients with inflammatory myopathies or dystrophies. There are several, complex molecular pathways; however, the comparison of expression profiles in patients with different muscle disorders permits the delineation of disease-specific patterns. It is hoped that novel approaches for treating the inflammatory myopathies and dystrophies can be derived from intimate knowledge of the pathways involved in each disease, and the key molecules that provide cross-talk between pathways.