Hyperthyroidism and Addison's disease in a patient with myotonic dystrophy

A 53-year-old man had myotonic dystrophy, hyperthyroidism, and Addison's disease, an association not previously reported, to our knowledge. In the literature, at least five cases of hyperthyroidism associated with myotonic dystrophy have been described, but none also had Addison's disease. The presence of thyroid anti-microsomal antibodies and anti-adrenal antibodies suggests that the two endocrine disorders may be autoimmune. In our case, the treatment of the two endocrinopathies caused a reduction of myotonic symptoms.