Tuesday, November 27, 2018

MEF2C haploinsufficiency syndrome

Inspired by a patient

Vrečar I, Innes J, Jones EA, Kingston H, Reardon W, Kerr B, Clayton-Smith J, Douzgou S. Further Clinical Delineation of the MEF2C Haploinsufficiency Syndrome: Report on New Cases and Literature Review of Severe Neurodevelopmental Disorders Presenting with Seizures, Absent Speech, and Involuntary Movements. J Pediatr Genet. 2017 Sep;6(3):129-141

Mutations in the MEF2C ( myocyte enhancer factor 2 ) gene have been established as a cause for an intellectual disability syndrome presenting with seizures, absence of speech, stereotypic movements, hypotonia, and limited ambulation. Phenotypic overlap with Rett's and Angelman's syndromes has been noted. Following the first reports of 5q14.3q15 microdeletions encompassing the MEF2C gene, further cases with point mutations and partial gene deletions of the MEF2C gene have been described. We present the clinical phenotype of our cohort of six patients with MEF2C mutations and compare our findings with previously reported patients as well as with a growing number of genetic conditions presenting with a severe neurodevelopmental, Rett-like, phenotype. We aim to add to the current knowledge of the natural history of the "MEF2C haploinsufficiency syndrome" as well as of the differential diagnosis, clinical management, and genetic counseling in this diagnostically challenging group of patients.

Rocha H, Sampaio M, Rocha R, Fernandes S, Leão M. MEF2C haploinsufficiency syndrome: Report of a new MEF2C mutation and review. Eur J Med Genet. 2016 Sep;59(9):478-82.


MEF2C haploinsufficiency syndrome is characterized by severe intellectual disability, epilepsy, stereotypic movements, minor dysmorphisms and brain abnormalities. We report the case of a patient with a new MEF2C mutation, comparing his clinical and imaging features to those previously reported in the literature.

A 10 year-old boy first came to pediatric neurology clinic at the age of 11 months because of severe psychomotor delay, without regression. He presented generalized hypotonia, poor eye contact, hand-mouth stereotypies, strabismus and minor facial dimorphisms. Epileptic seizures started at 26 months of age and were refractory. Brain MRI showed a slight increase in periventricular white matter signal and globally enlarged CSF spaces. Molecular analysis revealed a de novo, pathogenic and causative MEF2C mutation.

MEF2C haploinsufficiency syndrome was recently recognized as a neurodevelopmental disorder. Severe intellectual disability with inability to speak and epilepsy are universal features in patients with MEF2C mutations, although mild cognitive and speech disorders have been reported to occur in patients with duplications. Epilepsy might be absent in patients with partial deletions. Abnormal movement patterns are very common in patients with MEF2C haploinsufficiency. Delayed myelination seems to be more commonly observed in patients with MEF2C mutations, while malformations of cortical development were only reported in patients with microdeletions. Although MEF2C haploinsufficiency prevalence is yet to be determined, it should be considered in the differential diagnosis of patients with severe intellectual disability and Rett-like features.

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