Lambert-Eaton myasthenic syndrome occurring as a paraneoplastic manifestation of small cell lung carcinoma involves antibodies directed against which target?

• A Nicotinic acetylcholine receptors at the neuromuscular junction
• B Acetylcholinesterase in the synaptic cleft
• C Voltage-gated potassium channels on postsynaptic membrane
• D Voltage-gated calcium channels on presynaptic nerve terminals ✓

Explanation

Lambert-Eaton syndrome involves autoantibodies against presynaptic voltage-gated calcium channels (VGCC), which impair acetylcholine release from motor nerve terminals. This is distinct from myasthenia gravis, where antibodies target postsynaptic nicotinic ACh receptors. The syndrome is characterized by proximal muscle weakness that improves with repetitive activity, unlike MG.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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