Myotonic dystrophy associated with thyroid disease

Two patients with hereditary, clinical, electromyographical and histological data typical of myotonic dystrophy are discussed. In both there was a thyroid disorder. The first patient had primary hypothyroidism, and the second a non-toxic multinodular goiter which necessitated total thyroidectomy. The EMG findings and the muscle histopathology of both patients are commented on and compared with the changes described in hypothyroidism. The disease processes in both patients are also discussed in relation to the muscle and metabolic changes described in myotonic dystrophy. The coexistence of these two diseases is not explicable in the light of present knowledge on the basis of a known genetic predisposition. Only two similar cases of myotonic dystrophy and hypothyroidism have been reported.