A 38-year-old woman has severe oropharyngeal and neck weakness with marked ptosis that worsens through the day. AChR antibodies are negative. Repetitive nerve stimulation shows decrement, and antibodies against muscle-specific tyrosine kinase are positive. Which statement about her condition is correct?
- A Her weakness will respond poorly to all forms of immunotherapy
- B Thymoma is present in more than half of such patients
- C She is unlikely to have thymic pathology and thymectomy is not routinely indicated ✓
- D Repetitive stimulation characteristically shows incremental response rather than decrement
Correct answer: C. She is unlikely to have thymic pathology and thymectomy is not routinely indicated
Explanation
MuSK-positive myasthenia gravis predominantly affects ocular, bulbar, and neck muscles, often with prominent atrophy, and is typically seronegative for AChR antibodies. Unlike AChR-positive disease, it is not associated with thymic hyperplasia or thymoma, so thymectomy is not routinely recommended. Incremental response on repetitive stimulation is the hallmark of Lambert-Eaton syndrome, not MuSK-MG, and MuSK-MG does respond to immunotherapy including rituximab.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.