Cryptogenic dyspnea: Report of myasthenia gravis presenting solely as unexplained dyspnea and review of the literature

Myasthenia gravis commonly presents as generalized muscle weakness. It is rare for the disease to selectively affect the respiratory muscles. We present the first report of unexplained dyspnea caused by myasthenia gravis, presenting solely as isolated respiratory muscle weakness. Two patients presented with a normal physical examination and radiologic studies and displayed restrictive spirograms with significantly reduced maximal voluntary ventilation (MVV) and respiratory muscle pressures. A review of the respiratory manifestations of myasthenia gravis and the current view on pathophysiology, diagnosis, and treatment are presented. The clinical clues to the diagnosis are highlighted and serve to remind clinicians of an uncommon cause of a common clinical problem.