A 52-year-old woman comes to the hospital because of progressive weakness and dyspnea. She does not have chest pain, or a history of recent illness. She is in temporarly visit of her son and she forgot to bring her medications. She has smoked two packs of cigarettes daily for 25 years. She appears fatigued. Examination shows drooping of the upper eyelids. There is diminished motor strength in the upper extremities. Sensation and reflexes are intact. Arterial blood gas obtained on room air shows pH 7.32; PaCO₂ is 52 mm Hg, PaO₂ is 72 mm Hg, and HCO₃ is 26 mEq/L. Bedside spirometry demonstrates decreased forced vital capacity. A pathologic process involving which of the following structures is the most likely cause of this patient's shortness of breath?

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Quizplus · Accepted Answer

Eductional Objective: Myasthenia gravis is characterized by autoantibodies against postsynaptic nicotinic acetylcholine receptors at the neuromuscular junction, which result in receptor degradation.  Patients typically have extraocular, bulbar, and facial weakness that worsens with activity.  In severe cases, the respiratory muscles may be affected, leading to hypoventilation and respiratory failure.

A 52-Year-Old Woman Comes to the Hospital Because of Progressive