CPAP therapy reverses weakness of myasthenia gravis: role of obstructive sleep apnea in paradoxical weakness of myasthenia gravis.

Fatigability after exercise and restoration of strength by rest are clinical hallmarks of myasthenia gravis (MG). These unique features are originated from a reduced safety factor, which is related to a defect of acetylcholine receptor, and post-exercise exhaustion of neuromuscular junction transmission. Therefore, most patients with MG feel recharged muscle strength and show normal muscle power after nocturnal sleep. As such, worsening of MG symptoms during nighttime is usual. However, in very rare cases, some patients with MG complain fatigability and weakness in the morning, so called "paradoxical weakness (PW)." We report two MG patients with typical PW, diagnosed with OSA by polysomnography. CPAP therapy successfully improved their morning symptoms and quality of life. So far, the detailed mechanism of PW in MG is unknown; however, our report highlights the possible role of sleep disorders in developing a PW in MG and the therapeutic target for life quality of MG.