A 58-year-old man with small cell lung carcinoma develops proximal muscle weakness, hyporeflexia, and autonomic dysfunction. Electromyography shows augmentation of muscle action potential on repetitive nerve stimulation. Which antibody is most likely responsible for this paraneoplastic syndrome?
- A Anti-Hu (ANNA-1)
- B Anti-VGCC (voltage-gated calcium channel antibody) ✓
- C Anti-Yo (Purkinje cell antibody)
- D Anti-NMDAR antibody
Correct answer: B. Anti-VGCC (voltage-gated calcium channel antibody)
Explanation
Lambert-Eaton myasthenic syndrome (LEMS) is a paraneoplastic disorder most commonly associated with small cell lung carcinoma. Anti-VGCC antibodies impair presynaptic calcium influx, reducing acetylcholine release; repetitive stimulation paradoxically augments responses, distinguishing LEMS from myasthenia gravis. Anti-Hu causes paraneoplastic sensory neuropathy/encephalomyelitis, while anti-Yo causes cerebellar degeneration.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.