Unusual Neurodevelopmental Triad: Developmental and Epileptic Encephalopathy With Spike-Wave Activation in Sleep, Narcolepsy Type 1, and Mosaic Turner Syndrome

Introduction Developmental and epileptic encephalopathy with spike wave activation in sleep (DEE-SWAS), narcolepsy type 1 (NT1), and Turner syndrome (TS) have been independently described in pediatric populations. However, their simultaneous occurrence has not been reported. We present, to our knowledge, the first documented case of this triad in a 13-year-old female patient, highlighting the complex diagnostic interplay between cortical excitability, sleep architecture, and genetics. Case Description The patient had a history of coarctation of the aorta and was diagnosed with focal epilepsy at age 4 years. At 13 years, she developed worsening nocturnal seizures and excessive daytime sleepiness. Continuous electroencephalography demonstrated bilateral spike-wave activation occupying >85% of non-REM sleep, confirming DEE-SWAS. Following corticosteroid and clobazam therapy, electrographic abnormalities resolved, though clinical seizures persisted at low frequency. Subsequently, she developed recurrent “drop attacks” characterized by emotional triggers, preserved consciousness, and rapid recovery. These symptoms are hallmarks of cataplexy rather than atonic seizures. Polysomnography and Multiple Sleep Latency Testing were nondiagnostic, likely confounded by sedating antiseizure and psychotropic medications. Cerebrospinal fluid orexin-A was reduced (165 pg/mL; normal >200 pg/mL), supporting early hypocretin deficiency. Chromosomal analysis revealed 6% mosaic 45,X monosomy, confirming mosaic TS. Discussion DEE-SWAS-related sleep disruption and antiseizure polypharmacy likely obscured early NT1 features, thus delaying diagnosis. This unprecedented coexistence underscores that distinguishing cataplexy from epileptic atonia represents quite a challenge to the clinician. This is particularly true in patients with established epilepsy, where drop attacks are easily misattributed. Recognition of this triad is essential for multidisciplinary management, patient safety, and long-term outcomes.