An Electron Microscopic Study of Myotonic Dystrophy

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Abstract
FAMILIAL myotonic dystrophy usually has its onset in adult life and shows myotonia and muscle wasting as its principal characteristics. A high incidence of cataracts, frontal baldness, hypothyroidism, testicular or ovarian atrophy, and diabetes mellitus support the multisystem nature of the disease. The skeletal muscle manifestations have been of principal interest to neurologists. MacDermot1 and Coers2 describe abnormalities of the neuromuscular junction similar to those seen in denervation of muscle. Daniel and Strich3 report proliferation of intrafusal fibers in muscle spindles. However, the main histopathology lies in the skeletal muscle fibers themselves. Variation in individual fiber size, loss of fibers with rare Fig 1.—Left, A portion of hypertrophic fiber with usual cross striations fills the upper field. In the lower portion of the figure, a large area of degeneration has replaced fibrils with alternating zones of dense and light material. To the right of the