A 62-year-old Caucasian male complains of occasional episodes of double vision over the last two months. He also has intermittent difficulty swallowing. The symptoms typically occur at the end of the day and go away after a short nap. He denies any headaches, nausea, vomiting, imbalance, or falls. Past medical history is significant for hypertension, hyperlipidemia, type 2 diabetes mellitus, and mild intermittent asthma. He also had a transient ischemic attack five years ago and underwent a left carotid endarterectomy. Current medications include metformin, glipizide, lisinopril, atorvastatin, hydrochlorothiazide, and aspirin. He also uses an albuterol inhaler as needed for wheezing and shortness of breath. He is a current smoker with a 35 pack-year smoking history. His blood pressure is 134/78 mmHg and heart rate is 86/min. On examination, there is mild left ptosis. Which of the following is the most likely cause of this patient's complaints?

Question

A 62-year-old Caucasian male complains of occasional episodes of double vision over the last two months.  He also has intermittent difficulty swallowing.  The symptoms typically occur at the end of the day and go away after a short nap.  He denies any headaches, nausea, vomiting, imbalance, or falls.  Past medical history is significant for hypertension, hyperlipidemia, type 2 diabetes mellitus, and mild intermittent asthma.  He also had a transient ischemic attack five years ago and underwent a left carotid endarterectomy.  Current medications include metformin, glipizide, lisinopril, atorvastatin, hydrochlorothiazide, and aspirin.  He also uses an albuterol inhaler as needed for wheezing and shortness of breath.  He is a current smoker with a 35 pack-year smoking history.  His blood pressure is 134/78 mmHg and heart rate is 86/min.  On examination, there is mild left ptosis.  Which of the following is the most likely cause of this patient's complaints?

Quizplus · Accepted Answer

Explanation: This patient's presentation is most consistent with myasthenia gravis, which is a disease of the neuromuscular junction. The classic feature of myasthenia gravis is fluctuating muscle weakness that worsens throughout the course of the day. Most patients first notice double vision and ptosis that worsens at the end of the day, which is caused by weakness in the extraocular muscles. The next most common muscles involved are the bulbar muscles resulting in dysphagia and dysarthria. Proximal limb weakness is found less frequently. Fatigability of muscle function is the key to differentiating myasthenia gravis from other similar disorders. Myasthenia gravis is an autoimmune disease caused by autoantibodies against the acetylcholine receptor. There is a known association between myasthenia gravis and thymoma. (Choice A) Statin medications are infamous for leading to myopathy. However, it would be atypical for statin-induced myopathy to only involve the ocular and bulbar muscles, and the worsening of symptoms throughout the course of the day would be atypical. Rarely, statin medications can lead to new or worsening myasthenic symptoms. (Choice C) This patient's diabetes places him at risk for developing peripheral neuropathy. However, peripheral neuropathy typically first affects the nerves in the feet since they are the longest in the body. (Choice D)Lower motor neuron disease generally does not worsen throughout the course of the day and improve with rest. (Choice E) This patient is at risk of recurrent transient ischemic attacks given his prior history and numerous cardiovascular risk factors. However, the fact that he is having daily symptoms is not typical for transient ischemic attacks. Educational objective: Myasthenia gravis is an autoimmune disease caused by autoantibodies that attack the acetylcholine receptors in the neuromuscular junction. The ocular and bulbar muscles are the most commonly involved muscles groups, and the classic presentation consists of progressive muscular weakness throughout the day that improves with rest.

A 62-Year-Old Caucasian Male Complains of Occasional Episodes of Double