Abstract Details

Title MuSK Antibody Positive Myasthenia Gravis Presenting with Bilateral Vocal Cord Abduction Paralysis: A Case Report and Literature Review

Topic Neuromuscular and Clinical Neurophysiology (EMG)

Presentation(s) P3 - Poster Session 3 (12:00 PM-1:00 PM)

Poster/Presentation
Number 1-005

Objective To present the case of a patient with muscle-specific tyrosine kinase (MuSK) antibody positive myasthenia gravis presenting with hoarse voice secondary to bilateral vocal cord abduction paralysis and review the literature on MuSK myasthenia gravis.

Background Approximately 39-49% of patients with previously diagnosed acetylcholine receptor antibody-negative myasthenia gravis have been found to be MuSK antibody positive. These patients have a presentation that typically includes oculobulbar weakness, poorer response to cholinesterase inhibitors and are higher risk for acute clinical decompensation that necessitates plasma exchange (PLEX). MuSK patients can require more aggressive maintenance immunosuppression earlier on to maintain stability, often with rituximab.

Design/Methods We report the case of a 45 year old female who presented with months of worsening hoarseness and exertional dyspnea that was discovered to be secondary to limited abduction of vocal cords bilaterally. Exam revealed ophthalmoparesis and fatigueable proximal muscle weakness. She was found to have elevated MuSK autoantibodies which, along with evidence of neuromuscular junction transmission defect on nerve conduction studies, confirmed the diagnosis of MuSK myasthenia gravis. She experienced no improvement with pyridostigmine and decompensated despite receiving oral steroids, requiring intubation. Fortunately, she improved with PLEX and has since been doing well on rituximab therapy.

Results NA

Conclusions Dysphonic voice with hoarse quality secondary to vocal cord abduction paralysis is a rare presentation of myasthenia gravis, as opposed to the typical flaccid dysarthria seen in bulbar myasthenia, and should raise suspicion for MuSK antibody positivity. MuSK myasthenia gravis cases can be more refractory to treatment with cholinesterase inhibitors and are more likely to cause exacerbations and myasthenia crisis. Therefore, early and accurate diagnosis with appropriate antibody testing is imperative to avoid delays in treatment to prevent potentially life-threatening outcomes.

Authors/Disclosures
Ashley Santilli, MD (Mayo Clinic) PRESENTER	Dr. Santilli has nothing to disclose.
Derek W. Stitt, MD (Mayo Clinic)	Dr. Stitt has nothing to disclose.

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