A 60-year-old woman with small cell lung cancer develops proximal muscle weakness with augmented strength after brief exercise and positive anti-VGCC antibodies. This paraneoplastic syndrome is:

• A Myasthenia gravis — antibodies against AChR
• B Polymyositis — T-cell-mediated muscle fiber necrosis
• C Eaton-Lambert syndrome — antibodies against AChE
• D Lambert-Eaton myasthenic syndrome — antibodies against presynaptic voltage-gated calcium channels (VGCC) ✓

Explanation

Lambert-Eaton myasthenic syndrome (LEMS) is most commonly associated with small cell lung cancer and is caused by autoantibodies against presynaptic P/Q-type voltage-gated calcium channels, impairing ACh release. Clinically: proximal weakness that transiently improves with repetitive stimulation (post-tetanic potentiation) and reduced deep tendon reflexes. Unlike myasthenia gravis (postsynaptic AChR antibodies), strength augments after repeated effort in LEMS.

Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.