Association of primary hyperparathyroidism with myotonic dystrophy in two patients.

In two patients primary hyperparathyroidism developed in association with myotonic dystrophy (MyD). Both patients had solitary adenoma, and the adenomas were surgically removed. After the operation, subjective improvement of muscle weakness was found in one patient. Because parathyroid hormone secretion is regulated by extracellular calcium concentration and because abnormalities in transmembrane calcium transport are thought to play a role in the pathogenesis of MyD, the concurrence of these rather rare disorders in two patients raises the possibility that abnormalities in transmembrane calcium transport may underlie the development of primary hyperparathyroidism in patients with MyD. Although further studies are needed to clarify the possible link between these two disorders, the present study emphasizes the importance of evaluation of parathyroid function in patients with MyD.