Since the first description of primary adrenocortical insufficiency by Thomas Addison in 1855 several large series of patients with Addison's disease have been published. The common signs and symptoms include: weakness, hyperpigmentation, weight loss, gastrointestinal complaints, and hypotension. It is rare for patients with Addison's disease to present with musculoskeletal symptoms including flexion contractures, hyperkalaemic neuromyopathy, Guillain-Barre syndrome, migratory myalgia, sciatica-like pain, and low back pain. Myopathy has not been previously described in Addison's disease. Herein we report a patient presenting with severe hyponatraemia and myopathy which resolved after steroid replacement therapy.