Developmental and epileptic encephalopathies (DEEs) are a heterogeneous group of severe disorders that are characterized by early-onset, refractory seizures and developmental slowing or regression. Based on the underlying genetic change, there are over 50 types of DEEs. DEE 56, also known as epileptic encephalopathy, early infantile, 56 is a relatively newer neurodevelopmental disorder caused by de novo pathogenic variations in YWHAG gene and inherited in an autosomal dominant manner. The affected patients exhibit early-onset epilepsy, intellectual disability, motor developmental delay, speech impairment, and sometimes, behavioral problems, scoliosis, mild facial dysmorphism and ataxia. However, the disorder has great clinical heterogeneity, as some patients may have a mild phenotype, with epilepsy alone with normal development. More recently, the spectrum of clinical features caused by DEE 56 have been expanded to mild myoclonic epilepsy and febrile seizures (Ye et al., 2021). So far (Jan 2023), 15 pathogenic variants in 25 patients are found in the literature in YWHAG causing DEE 56. More individuals will likely be found in the future as genetic testing is more commonly used for undiagnosed epilepsy cases.
YWHAG