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•    Prevalence is unknown.
•    X-linked recessive (XLR) inheritance: females can be healthy carriers and males can be affected.
•    Mainly developmental delay (language and psychomotor development) and/or autism spectrum disorder (ASD).
•    Often seizures: clonic, tonic, generalized tonic-clonic and/or atypical absences, which can become drug-resistant. EEG can show epileptiform activities (spike and/or spike-wave complexes).
•    Brain MRI is usually normal.