A 65-year-old man with a 50 pack-year smoking history presents with a 3 cm right hilar mass on CT. He reports proximal leg weakness that improves with repeated activity. Which paraneoplastic syndrome is most likely associated with this presentation?
- A Syndrome of inappropriate antidiuretic hormone secretion
- B Humoral hypercalcemia of malignancy
- C Lambert-Eaton myasthenic syndrome ✓
- D Ectopic Cushing syndrome
Correct answer: C. Lambert-Eaton myasthenic syndrome
Explanation
Lambert-Eaton myasthenic syndrome is a paraneoplastic syndrome strongly associated with small cell lung cancer. It is characterized by proximal muscle weakness that improves with repeated effort, unlike myasthenia gravis which worsens. The autoantibodies target presynaptic voltage-gated calcium channels. SIADH and ectopic Cushing syndrome are also seen in small cell carcinoma but do not cause this pattern of weakness. Hypercalcemia is typical of squamous cell carcinoma.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.