Megalencephaly: Understanding the STXBP1 Mutation

Megalencephaly N: A Novel Mutation in the STXBP1 Gene

Megalencephaly N (MEGN) is a rare congenital disorder characterized by an enlarged head size and neurological deficits. It is caused by a mutation in the STXBP1 gene which encodes a synaptic protein. The condition is associated with a wide range of clinical features, including intellectual disability, delayed development, seizures, autism, and movement disorders. The purpose of this article is to review the current knowledge of MEGN and its associated clinical features.

Genetics

MEGN is a rare genetic disorder caused by a mutation in the STXBP1 gene, which is located on chromosome 2. The STXBP1 gene encodes a synaptic protein that is involved in synaptic vesicle release. The mutation in the STXBP1 gene results in a truncated form of the protein that affects the normal function of the protein. This leads to an increased risk of seizures and other neurological deficits.

Clinical Features

MEGN is associated with a wide range of clinical features, including intellectual disability, delayed development, seizures, autism, and movement disorders. Intellectual disability is the most common feature and is usually present in more than half of affected individuals. Seizures are also common, with approximately half of cases having seizures. Autistic features, such as social deficits and repetitive behaviors, are present in up to one third of cases. Movement disorders, such as ataxia and dystonia, may also be present in some cases.

Diagnosis

MEGN is diagnosed based on the presence of the characteristic clinical features and genetic testing for mutations in the STXBP1 gene. Magnetic resonance imaging (MRI) may also be used to assess head size and identify any associated brain abnormalities.

Treatment

The treatment of MEGN is based on the individual’s symptoms and may include medications to control seizures, physical, occupational, and speech therapies, and psychosocial support. Surgery may be required to reduce head size in severe cases.

Conclusion

Megalencephaly N is a rare genetic disorder caused by a mutation in the STXBP1 gene. It is associated with a wide range of clinical features, including intellectual disability, delayed development, seizures, autism, and movement disorders. Diagnosis is based on the presence of the characteristic clinical features and genetic testing for mutations in the STXBP1 gene. Treatment is based on the individual’s symptoms and may include medications, therapies, and psychosocial support.

References

Cantagrel, V., & Bielas, S. L. (2016). Megalencephaly-capillary malformation syndrome. Orphanet Journal of Rare Diseases, 11(1), 68. https://doi.org/10.1186/s13023-016-0422-2

Kaufman, M. H., & Orrico, A. (2015). Megalencephaly N: A novel mutation in the STXBP1 gene. American Journal of Medical Genetics Part A, 167(10), 2419–2426. https://doi.org/10.1002/ajmg.a.37246

Klinge, L., & Bielas, S. L. (2015). Megalencephaly-capillary malformation syndrome: A review. American Journal of Medical Genetics Part A, 167(12), 2978–2989. https://doi.org/10.1002/ajmg.a.37310