Developmental and epileptic encephalopathy-31A (DEE31A) is an autosomal dominant neurologic disorder characterized by the global developmental delay apparent in early infancy. Most individuals have onset of various types of refractory seizures in the first months or years of life, which exacerbates the psychomotor deficits. Patients have hypotonia and profound intellectual disability with absent speech and inability to walk or ataxic gait. Some patients may have additional features, including dysmorphic features or cortical visual impairment (summary by the EuroEPINOMICS-RES Consortium et al., 2014 and Deciphering Developmental Disorders Study, 2015). For a general phenotypic description and a discussion of genetic heterogeneity of DEE, see 308350.