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Phenotypic Differences in 2 Unrelated Cases Carrying Identical DOK7 Mutations
Véronique Bissay1, Ricardo A Maselli2
1Department of Neurology, Center for Neurosciences, UZ Brussel, Vrije Universiteit Brussel (VUB), Brussels, Belgium.
Journal of Clinical Neuromuscular Disease
|August 28, 2019
Summary
Mutations in the Dok-7 gene cause congenital myasthenic syndrome (CMS) with limb-girdle weakness. These cases show variable symptoms and no clear genotype-phenotype link in DOK7-related CMS.
Area of Science:
- Neurology
- Genetics
- Molecular Biology
Background:
- Congenital myasthenic syndrome (CMS) is a group of inherited disorders affecting neuromuscular transmission.
- Mutations in the Dok-7 gene (DOK7) are a known cause of CMS, typically presenting with limb-girdle (LG) muscle weakness.
- Clinical presentation of DOK7-related CMS is known to be heterogeneous.
Observation:
- Two unrelated adult patients with limb-girdle CMS were identified.
- Both patients harbored compound heterozygous pathogenic variants in the DOK7 gene: c.1124_1127dupTGCC (P.Ala378Serfs*30) and c.480C>A (p.Tyr160*).
Findings:
- Despite shared DOK7 mutations, clinical phenotypes varied significantly between patients.
- One patient exhibited severe proximal and distal lower extremity weakness.
- The other patient presented with severe bulbar and respiratory deficits, requiring significant supportive care.
Implications:
- These findings highlight the lack of a strong genotype-phenotype correlation in DOK7-related CMS.
- The study suggests that geographic, genetic, and ethnic factors do not appear to strongly influence the phenotype of DOK7-related LG CMS.
- Understanding this variability is crucial for accurate diagnosis and management of congenital myasthenic syndromes.
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