skip to main content

Seronegative Myasthenia Gravis – LRP4 Antibodies — SCE Neurology MCQ

Instant feedback + full explanation. One question, done properly.

ModeratePeripheral Neuropathy & NeuromuscularSeronegative Myasthenia Gravis – LRP4 AntibodiesSCE Neurology

A 40-year-old woman presents with episodic double vision and ptosis, particularly in the evening. Ice pack test shows improvement in ptosis. Repetitive nerve stimulation shows a 15% decrement at 3 Hz. AChR antibodies are negative. MuSK antibodies are negative. CT chest shows no thymoma. What further antibody test should be considered?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: C — Anti-LRP4 antibodies

In seronegative myasthenia gravis (negative for both AChR and MuSK antibodies), testing for anti-LRP4 (lipoprotein receptor-related protein 4) antibodies should be considered. LRP4 antibodies are found in approximately 2–50% of double-seronegative MG cases depending on the assay. Some patients previously classified as seronegative may also have low-affinity AChR antibodies detectable only by cell-based assay. B: VGCC antibodies are for Lambert-Eaton syndrome. C: Anti-GAD65 is for stiff person syndrome. D: Anti-NMDA receptor antibodies are for autoimmune encephalitis. E: Anti-Hu is for paraneoplastic syndromes.

Reference: ABN MG Guidelines (2025); MGFA International Consensus Guidance (2020)