A 60-year-old male with a heavy smoking history presents with proximal muscle weakness that improves with repeated muscle contraction. What underlying malignancy is most strongly associated?
Answer and explanation
Correct answer: B. Small cell lung carcinoma
- Step 1: Proximal muscle weakness that characteristically improves following brief exercise indicates Lambert-Eaton myasthenic syndrome (LEMS).
- Step 2: LEMS is a paraneoplastic disorder resulting from autoantibodies against presynaptic voltage-gated calcium channels, strongly associated with small cell lung carcinoma.
Answer
Small cell lung carcinoma.
Why not the others: Renal cell carcinoma causes paraneoplastic erythrocytosis and hypercalcemia but is not associated with LEMS. Colorectal adenocarcinoma has no known association with Lambert-Eaton myasthenic syndrome. Cutaneous melanoma does not typically produce presynaptic neuromuscular junction paraneoplastic autoantibodies.
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