A 58-year-old man with small cell lung carcinoma develops proximal muscle weakness and absent deep tendon reflexes that improve with repeated activity. Antibodies against which antigen are responsible for this paraneoplastic syndrome?
- A Anti-Hu (ANNA-1)
- B Voltage-gated calcium channel (VGCC) antibodies ✓
- C Anti-Ri (ANNA-2)
- D Anti-amphiphysin antibodies
Correct answer: B. Voltage-gated calcium channel (VGCC) antibodies
Explanation
Lambert-Eaton myasthenic syndrome (LEMS) is associated with small cell lung carcinoma and is caused by antibodies against presynaptic voltage-gated calcium channels (VGCC), impairing acetylcholine release. Clinically, strength paradoxically improves with repeated stimulation (post-tetanic facilitation), distinguishing it from myasthenia gravis. Anti-Hu causes paraneoplastic sensory neuropathy/encephalomyelitis, anti-Ri causes opsoclonus-myoclonus, and anti-amphiphysin causes stiff-person syndrome.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.