Neurodevelopmental disorder with hypotonia and variable intellectual and behavioral abnormalities (NEDHIB) is characterized by early-onset hypotonia, delayed walking, poor speech, and impaired intellectual development. Additional features may include feeding difficulties, dysmorphic features, and visual defects. Brain imaging tends to show delayed myelination, thin corpus callosum, and/or enlarged ventricles. The severity of the disorder is highly variable; initial evidence suggests that the severity may depend on the type of mutation (summary by Haijes et al., 2019).