An Unexpected Cause of Asymmetric Weakness and Atrophy in an Adult.
Document Type
Conference Proceeding - Restricted Access
Publication Date
5-9-2025
Abstract
Congenital myasthenic syndromes classically present with fatigable weakness, ptosis and delayed motor milestones. A limb girdle type of congenital myasthenia can be difficult to diagnose and can often be mistaken for a myopathy or a muscular dystrophy due to the lack of ocular symptoms such as ptosis and diplopia. Congenital myasthenia presenting with limb girdle weakness has previously been described in autosomal recessive syndromes associated with mutations in DOK7, COLQ, GFPT1, DPAGT1. However, limb girdle weakness has never been described with an autosomal dominant slow channel congenital myasthenia.
A 39-year-old male presents with progressive bilateral arm weakness for 2 years. Even though arm weakness started 2 years ago, he mentioned having neck weakness as an infant. He had shoulder abduction, wrist extension and finger extension weakness with muscle atrophy on exam. He was also noted to have bilateral scapular winging and a long face with hallowed temples. Initial nerve conduction study was normal although a double peak appearance of CMAPs were noted. Electromyogram showed a myogenic pattern with early recruitment, decreased amplitude and duration of the MUAPs in multiple upper extremity muscles. CK was normal. Genetic testing was positive for a heterogenous mutation within the CHRNA1 gene that is classically associated with a slow channel congenital myasthenic syndrome. The patient's immediate family was also tested and the heterogenous mutation was found to be de novo. Repeat electrodiagnostic studies revealed decrement in amplitudes confirming the diagnosis.
The patient was then started on fluoxetine 40 mg daily for treatment with significant improvement in weakness.
Slow channel congenital myasthenic syndrome can present with limb girdle weakness. It is important to obtain broad genetic testing when suspecting a genetic/congenital cause of weakness to avoid missing the diagnosis. Broad genetic testing in our patient resulted in identifying the correct diagnosis and initiating treatment promptly.
Recommended Citation
Komanduru W, Ebright M. An unexpected cause of asymmetric weakness and atrophy in an adult. Presented at: Research Day Corewell Health West; 2025 May 9; Grand Rapids, MI.
Comments
2025 Research Day Corewell Health West, Grand Rapids, MI, May 9, 2025. Abstract 1673