A 55-year-old woman with a lung mass develops proximal muscle weakness with characteristic electromyographic improvement on repeated stimulation. Which antibody mediates this paraneoplastic syndrome?

• A Anti-Yo antibodies
• B Antibodies against acetylcholine receptor
• C Anti-Hu antibodies
• D Antibodies against voltage-gated calcium channel ✓

Explanation

Lambert-Eaton myasthenic syndrome is caused by IgG against presynaptic P/Q-type voltage-gated calcium channels, reducing acetylcholine release at the neuromuscular junction; it is classically associated with small cell lung carcinoma. Myasthenia gravis involves postsynaptic acetylcholine receptor antibodies and fatigues rather than improves with repetition. Anti-Hu causes sensory neuropathy or encephalomyelitis and anti-Yo causes cerebellar degeneration.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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