Abstract
Four patients with hyperparathyroidism associated with myotonic dystrophy have been identified. All were females aged between 2 and 45 years. They were from three separate families, with two related patients being mother and daughter. In addition, one patient had medullary carcinoma of the thyroid and was diagnosed as having multiple endocrine adenomatosis, type 2A; another had an unspecified thyroid carcinoma; a third patient had neurofibromatosis. Our data suggest that myotonic dystrophy may somehow be associated with one or more of these disorders of neural crest origin.