A 26-year-old woman has severe fluctuating bulbar and neck weakness with mild ptosis; she has minimal limb fatigability and a poor symptomatic response to pyridostigmine. Thymus imaging is normal. Antibody testing should prioritise:

• A RyR antibodies
• B Titin antibodies
• C MuSK antibodies ✓
• D P/Q-type VGCC antibodies

Explanation

MuSK antibody-associated myasthenia gravis characteristically affects young women with prominent oculobulbar, facial and axial weakness, little thymic pathology, and a weaker response to cholinesterase inhibitors than AChR-positive disease, so MuSK serology is the key next test. Titin and RyR antibodies occur mainly in late-onset AChR-positive disease with thymoma, and P/Q-type VGCC antibodies indicate Lambert-Eaton syndrome.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.