USMLE-Rx Step 1 Qmax Challenge #1640

Check out today’s Step 1 Qmax Question Challenge.

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A 69-year-old smoker presents with double vision, lower extremity muscle weakness that improves with exertion, and diminished deep tendon reflexes. Results of neurologic, cardiovascular, and ophthalmologic examinations are negative. An X-ray of the chest is shown. A full cancer work-up reveals metastases throughout the body.

Which of the following is the most likely cause for this man’s diplopia and weakness?

A. Antibodies against presynaptic calcium channels at the neuromuscular junction
B. Autoantibodies to acetylcholine receptors at the neuromuscular junction
C. Autoimmune disease with anti-double-stranded DNA, anti-DNA, and anti-Smith antibodies
D. Inflammatory disorder of synovial joints with pannus formation
E. Reactivation of a peripheral subpleural parenchymal lesion and hilar lymph nodes

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