A 42-year-old woman comes to the physician because of progressive weakness for the past month. She has noticed increasing difficulty performing household chores and walking her dog. She has no other history of serious illness and takes no medications. She has smoked two packs of cigarettes daily for 25 years. Bilateral expiratory wheezes are heard at both lung bases. Examination shows drooping of the upper eyelids. There is diminished motor strength in the upper extremities. Sensation and reflexes are intact. The results of arterial blood gas analysis are as follows: Which of the following is most likely abnormal in this patient?

Question

A 42-year-old woman comes to the physician because of progressive weakness for the past month. She has noticed increasing difficulty performing household chores and walking her dog. She has no other history of serious illness and takes no medications. She has smoked two packs of cigarettes daily for 25 years. Bilateral expiratory wheezes are heard at both lung bases. Examination shows drooping of the upper eyelids. There is diminished motor strength in the upper extremities. Sensation and reflexes are intact. The results of arterial blood gas analysis are as follows:  Which of the following is most likely abnormal in this patient?

Quizplus · Accepted Answer

Eductional Objective: Myasthenia gravis is an autoimmune disorder caused by an autoantibody-mediated attack on the acetylcholine receptors of the postsynaptic neuromuscular junction, leading to a reduced number of acetylcholine receptors.  It is characterized by fatigable weakness of the skeletal muscles; respiratory failure can occur due to diaphragmatic weakness.

A 42-Year-Old Woman Comes to the Physician Because of Progressive