Some rare congenital and metabolic myopathies.

Four rare forms of inherited myopathy are reviewed. Nemaline myopathy shows certain well-defined clinical characteristics and rodlike structures derived from Z-band protein accumulate within the muscle fibers. Myotubular or centronuclear myopathy presents usually with infantile hypotonia and the majority of the muscle fibers demonstrate central nuclei surrounded by perinuclear halos, developmental arrest may well be followed by perinuclear degeneration. Glycogen storage disease due to acid maltase deficienty is now recognized as an occasional cause of late-onset myopathy. An unusual case of myopathy due to lipid storage in Type I muscle fibers is described.