Concomitant dermatomyositis and myasthenia gravis presenting with respiratory insufficiency.

We report a 28-year-old woman with a history of chronic immune-mediated hepatitis, in whom the simultaneous manifestation of dermatomyositis and myasthenia gravis resulted in severe neck extensor weakness and subacute respiratory insufficiency, followed by proximal muscle weakness and external ophthalmoplegia. Radiological signs of a thymoma were absent. The distinguishing clinical, electrophysiological, and biopsy findings are discussed.