Developmental delay with or without epilepsy (DEVEP) is a clinically heterogeneous neurodevelopmental disorder characterized by motor delay, speech delay, and variably impaired intellectual development apparent from infancy or early childhood. Hypotonia and behavioral abnormalities are common. About half of affected individuals develop various types of seizures that are not as severe as observed in the allelic disorder DEE5. In general, the phenotype is similar to but milder than DEE5. Some individuals with DEVEP have ataxia or nystagmus associated with cerebellar atrophy on brain imaging, indicating phenotypic overlap with the allelic disorder SPG91 (Morsy et al., 2023). In a study of 31 individuals with SPTAN1 mutations, Morsy et al. (2023) delineated 3 distinct phenotypic subgroups: DEE5; a milder phenotype of developmental delay with or without seizures (DEVEP); and pure or complicated spastic paraplegia/ataxia (SPG91). Syrbe et al. (2017) similarly emphasized the remarkably broad phenotypic spectrum of neurologic disorders associated with heterozygous SPTAN1 mutations in their cohort study.