Sleep Disordered Breathing Mimicking Myasthenia Crisis in a Patient with Myasthenia Gravis.

Myasthenia gravis (MG) can result in weakness of the respiratory muscles in 30% of patients. A life-threatening exacerbation, MG crisis can cause respiratory insufficiency requiring mechanical ventilation. Sleep disordered breathing (SDB) is seen in 40% to 60% of stable MG patients. Factors associated with SDB include age, male sex, obesity, and steroid use. Continuous positive airway pressure (CPAP) can reverse paradoxical weakness in MG patients with obstructive sleep apnea (OSA), but whether SDB can contribute to respiratory failure in MG and whether CPAP works in such patients remain unclear. This report presents a 54-year-old woman with MG with a history of 7 episodes of respiratory failure requiring mechanical ventilation. For each episode, she was treated for MG crisis using plasmapheresis and high-dose steroids. Later, OSA and obesity hypoventilation syndrome were confirmed by polysomnography with transcutaneous CO2 monitoring. Thereafter, the patient had no further recurrence of MG crisis for 5 years, using pyridostigmine and CPAP only.