Nationwide Survey of Association Between Fever and Epileptic Seizure in CDKL5 Deficiency Disorder Revealed Therapeutic Implications

OBJECTIVE: CDKL5 deficiency disorder (CDD) is a rare, severe developmental and epileptic encephalopathy. There is a pressing need to develop effective and sustainable therapeutic strategies. We aimed to investigate the causal association between febrile episodes and epileptic seizures for therapeutic implications in CDD patients. METHODS: The study was a nationwide, cross-sectional survey on CDD patients in China (ClinicalTrials.gov, NCT06663163). Detailed phenotypic and genotypic data were collected through an online questionnaire with uploaded original medical records, genetic testing results, and peri-fever seizure diaries. The primary outcome was changes in epileptic seizure frequency during and post-fever phases compared to a 1-month pre-fever phase based on seizure diaries. RESULTS: Between October 2024 and December 2024, we received 131 questionnaires. Forty-seven questionnaires were removed after excluding duplicates and missing data. Ultimately, 84 eligible participants with complete uploads were included, from 26 of 34 (76.5%) province-level regions in China. Among these, 47 (56.0%) patients had significant decreased seizure frequency only during febrile episodes, and 27 (32.1%) patients with daily seizures achieved at least a seizure-free day. Notably, 20 patients (23.8%) exhibited post-fever seizure reduction: 12 (25.5%) for 3 days to 1 week, and 6 (12.8%) for more than 2 weeks (maximum > 40 days). The effect was independent of patients' clinical and genetic characteristics. INTERPRETATION: Our findings, for the first time, revealed that fever-related seizure reduction is a distinctive and prevalent genotype-phenotype for CDD, thereby providing evidence for further fundamental research into the underlying mechanisms and offering potential clinical implications for seizure control in CDD.