Myopathy as the initial presentation of Addison's disease

A 16-year-old patient presented with three presyncopal episodes, muscle weakness, elevated creatine kinase and myopathic changes on electromyography, was diagnosed with Addison's disease through laboratory testing. Corticosteroid replacement produced marked improvement in muscle strength and normalized creatine kinase levels. In children, low corticosteroid state should be considered in the differential diagnosis of a myopathy, particularly in the setting of other signs and symptoms of adrenal insufficiency. To our knowledge, this is the first case report of a myopathy as the initial presentation of Addison's disease in this age group.