Developmental and epileptic encephalopathy-4 (DEE4) is a neurologic disorder characterized by the onset of tonic seizures in early infancy (usually in first months of life). In most cases, seizures increase in frequency and become refractory. Affected individuals have profoundly impaired psychomotor development with poor head control, limited or no ability to walk, spastic quadriplegia, and poor or absent speech. Brain imaging may show cortical atrophy and hypomyelination. EEG studies in the more severe cases show a burst-suppression pattern, consistent with a clinical diagnosis of Ohtahara syndrome, and/or hypsarrhythmia, consistent with a clinical diagnosis of West syndrome. Less severely affected individuals have later onset of seizures. [From OMIM]