Cytogenetic location of the POMGnT 1 gene is 1p34.1. MEB is caused by mutations of the protein O-linked mannose β1,2-N-acetylglucosaminyltransferase 1 (POMGnT1) gene. Pathogenic variants mutate the gene and lead to dysfunction of the POMGnT1 enzyme. Currently, there are 14 clinically identified mutations, the locations are dispersed and scattered throughout the POMGnT1 gene. Different mutations were observed in MEB patients from different countries, namely Finland, Sweden, Norway, Estonia, USA, Israel, Spain and Italy. From 14 non-Finnish patients, 9 different types of mutation were identified. The location of the mutation is slightly correlated with the severity of the symptoms in terms of brain structural abnormalities. Mutations close to the 5′ terminus of the POMGnT1 coding region lead to relatively more severe phenotype such as hydrocephalus. Mutations that occurred close to the 3′ terminus shows weaker symptoms. MEB is an autosomal recessive disease inherited from parents. Patients with MEB have two copies of a pathogenic variant in their gene. There will be a risk of having a child with MEB given that both parents are carriers of a pathogenic variant in their gene. The affected child inherits a mutated copy of the gene from each carrier parent. The chance of inheritance is 1 in 4 when both parents carry the pathogenic variant.
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Early myoclonic encephalopathy
Neurolathyrism
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