A 63-year-old man comes to the physician for the evaluation of difficulty walking for the last 6 months. He reports weakness in his lower legs that improves with exercise and throughout the day. Three months ago, he started adding flax seeds to his breakfast because he is frequently constipated. He has hypertension and type 2 diabetes mellitus. He has smoked 2 packs of cigarettes daily for the last 45 years. His current medications include enalapril and metformin. Vital signs are within normal limits. Examination shows dry mucous membranes. Muscle strength in the lower extremities is decreased. Sensation to pinprick and light touch is normal. Deep tendon reflexes are 1+ bilaterally. Active muscle contraction or repeated muscle tapping increases reflex activity. An x-ray of the chest shows an irregular, poorly demarcated mass at the right hilum. Which of the following is the most likely cause of this patient's muscle weakness?

Question

A 63-year-old man comes to the physician for the evaluation of difficulty walking for the last 6 months. He reports weakness in his lower legs that improves with exercise and throughout the day. Three months ago, he started adding flax seeds to his breakfast because he is frequently constipated. He has hypertension and type 2 diabetes mellitus. He has smoked 2 packs of cigarettes daily for the last 45 years. His current medications include enalapril and metformin. Vital signs are within normal limits. Examination shows dry mucous membranes. Muscle strength in the lower extremities is decreased. Sensation to pinprick and light touch is normal. Deep tendon reflexes are 1+ bilaterally. Active muscle contraction or repeated muscle tapping increases reflex activity. An x-ray of the chest shows an irregular, poorly demarcated mass at the right hilum.  Which of the following is the most likely cause of this patient's muscle weakness?

Quizplus · Accepted Answer

Eductional Objective: Lambert-Eaton myasthenic syndrome is characterized by antibodies against presynaptic voltage-gated calcium channels.  Patients develop progressive proximal muscle weakness with reduced/absent reflexes that predominantly involves the lower extremities.  The syndrome is often associated with malignancy, particularly small cell lung cancer.

A 63-Year-Old Man Comes to the Physician for the Evaluation