Abstract Details

Title An unusual case of MuSK- Congenital Myasthenic Syndrome

Topic Neuromuscular and Clinical Neurophysiology (EMG)

Presentation(s) Neuromuscular and Clinical Neurophysiology (EMG) Posters (7:00 AM-5:00 PM)

Poster/Presentation
Number 101

Objective

To describe a patient with a muscle-specific receptor tyrosine kinase (MuSK) gene mutation with atypical features, and contribute additional information to the known phenotypic spectrum of this condition.

Background Congenital myasthenic syndromes (CMS) are a heterogeneous group of hereditary disorders affecting neuromuscular transmission. CMS caused by Muscle Skeletal Receptor Tyrosine Kinase mutations (MuSK-CMS) are rare and have only been reported in a few families, with a more common onset in neonates and children and lack of response to anticholinesterase agents.

Design/Methods We describe the clinical features and evaluation in a female Puerto Rican patient with atypical MuSK-CMS.

Results A 41- year- old female presented with bilateral ptosis, horizontal ophthalmoparesis, jaw fatigue, dysphagia, and upper more than lower limb weakness. Her first symptoms were difficulty walking long distances and fatigue at age 17 years, which progressed to difficulty raising arms at age 29 years. At age 33 years she was hospitalized with worsening weakness and respiratory failure requiring mechanical ventilation. She was treated as a seronegative myasthenia gravis patient with IVIG, oral prednisone and pyridostigmine, with improvement of her symptoms. She continued to use pyridostigmine and BIPAP at night with an adequate response and no further hospitalizations. Anti-MuSK antibodies and anti- AChR antibodies (binding, blocking and modulating) were absent. Electrodiagnostic studies showed increased polyphasia without abnormal spontaneous activity in conventional EMG and abnormal jitter on Single Fiber EMG. Genetic testing for a possible CMS revealed a compound heterozygote mutation in the MuSK gene, c.2368G>A(p. Val790Met) and c. 2461 C>T (p.Leu821Met).

Conclusions This unique patient with MuSK-CMS and a compound heterozygote mutation showed clinical features similar to autoimmune MuSK-Myasthenia, with a favorable response to anticholinesterase agents. It is imperative to create awareness of the variable spectrum of MuSK-CMS to ensure proper identification and treatment, and prevent unnecessary interventions.

Authors/Disclosures
Alexandra Montalvo Acevedo, MD (University Pediatric Hospital) PRESENTER	Dr. Montalvo Acevedo has nothing to disclose.
Brenda Deliz Roldan	No disclosure on file
Carlos A. Luciano, MD, F�鶹��ýӳ�� (University of Puerto Rico School of Medicine)	Dr. Luciano has received personal compensation in the range of $500-$4,999 for serving on a Speakers Bureau for Sanofi-Genzyme. Dr. Luciano has received personal compensation in the range of $5,000-$9,999 for serving as an Expert Witness for SIMED. Dr. Luciano has received personal compensation in the range of $5,000-$9,999 for serving as an Expert Witness for Vazquez-Irizarry Law Office. The institution of Dr. Luciano has received research support from National Institutes of Health. Dr. Luciano has received personal compensation in the range of $100,000-$499,999 for serving as a Professor and Chair with University of Puerto Rico.

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