Neuropsychiatric Phenotype in a Patient with Neurodevelopmental Disorder with or Without Early-Onset Generalized Epilepsy (NEDEGE)

We report the oldest female identified to date with a pathogenic NBEA variant who has been followed longitudinally. She presented with a complex, diagnostically inconclusive psychiatric phenotype extending in adulthood and a suspected mild neurodevelopmental impairment. The 64-year-old patient experienced recurrent episodes of mental state decompensation characterized predominantly by persecutory and health-related delusional ideation and anxiety. Her most recent psychiatric diagnosis was mixed conversion disorder. Although she never underwent formal cognitive testing, mild intellectual disability was suspected based on her educational attainment, occupational history, and social functioning. Additionally, the patient presented with a likely coincidental tremor. A history of childhood epilepsy could not be confirmed, as detailed epilepsy records were unavailable. Furthermore, the patient declined neuroimaging, precluding assessment of a possible relationship with the identified EXT2 deletion. This case expands the currently recognized neuropsychiatric spectrum possibly associated with pathogenic NBEA variants, highlights the importance of extending phenotypic characterization in later adulthood, and underscores the value of longitudinal follow-up.