Abstract Details

Title Congenital Myasthenic Syndromes Diagnosed in Adulthood: A Case Series Exploring Genetic and Clinical Complexities

Topic Neuromuscular and Clinical Neurophysiology (EMG)

Presentation(s) P6 - Poster Session 6 (5:00 PM-6:00 PM)

Poster/Presentation
Number 9-019

Objective This series describes four adult-onset or late-recognized Congenital Myasthenic Syndromes (CMS) cases, emphasizing genetic heterogeneity, diagnostic challenges, and therapeutic implications.

Background Congenital Myasthenic Syndromes (CMS) are a group of inherited disorders caused by mutations affecting neuromuscular junction function. While most cases present in infancy or childhood, some remain unrecognized until adulthood due to mild or atypical symptoms. In adults, CMS may mimic seronegative myasthenia gravis, mitochondrial myopathies, or even limb-girdle muscular dystrophies, complicating diagnosis and delaying appropriate therapy.

Design/Methods We retrospectively reviewed four adults with genetically confirmed CMS (mutations in CHRNE, CHRND, and RAPSN). Clinical features, electrodiagnostic findings, genetic testing, and treatment responses were analyzed.

Results Presentations varied from longstanding ophthalmoplegia with minimal limb involvement to severe, progressive generalized weakness. Genetic testing identified pathogenic variants in CHRNE (two patients), CHRND (one patient), and RAPSN (one patient). Treatment responses were mutation-specific: pyridostigmine and beta-2 agonists benefited CHRNE cases, while 3,4-diaminopyridine improved the RAPSN phenotype. Appropriate recognition via genetic testing facilitated targeted therapy and improved quality of life.

Conclusions

Adult-onset or late-recognized CMS are often underdiagnosed or misclassified as seronegative myasthenia gravis. These cases highlight the importance of timely use of comprehensive neuromuscular genetic panels or exome sequencing leading to tailored treatments based on mutation subtype. Heightened awareness of this rare diagnosis can prevent unnecessary immunotherapy and improve clinical outcomes.

¹These two authors contributed equally to this work

Authors/Disclosures
Omnia M. Ali, MBBS (Suny Downstate Health Sciences neurology program) PRESENTER	Dr. Ali has nothing to disclose.
Andrew Porrazzo, MD	Dr. Porrazzo has nothing to disclose.
Yaacov Anziska, MD (SUNY-Downstate Medical Center)	Dr. Anziska has nothing to disclose.
Elizabeth M. Monohan, MD (Suny Downstate Medical Center)	Dr. Monohan has nothing to disclose.

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