NEXMIF is an X-linked gene involved in neurite outgrowth and neuronal development. While its precise molecular mechanism remains incompletely characterized, NEXMIF likely functions by regulating cell-cell adhesion through the N-cadherin signaling pathway and controlling expression of adhesion-related proteins 1. Loss-of-function variants in NEXMIF cause X-linked developmental and epileptic encephalopathy (DEE), characterized by severe intellectual disability in males and more variable presentations in females 2. Clinical features include developmental delay (99% of patients), seizures (83%), and comorbidities including myoclonic-atonic epilepsy, absence seizures with eyelid myoclonia, autism spectrum disorder, hypotonia, and behavioral abnormalities 23. Males typically present with more severe developmental impairment and language delays, while females more frequently develop refractory epilepsy 23. All pathogenic variants identified to date are loss-of-function mutations (premature stop codons or deleterious structural variants), and the degree of NEXMIF loss correlates with phenotype severity 23. While NEXMIF-associated DEE includes seizure risk, it is not currently associated with sudden unexplained death in epilepsy (SUDEP) unlike some other genetic DEEs 4. Early genetic diagnosis enables appropriate seizure management with antiepileptic drugs.