CDKL5 deficiency disorder and other infantile‐onset genetic epilepsies

Aim To differentiate phenotypic features of individuals with CDKL5 deficiency disorder (CDD) from those of individuals with other infantile‐onset epilepsies. Method We performed a retrospective cohort study and ascertained individuals with CDD and comparison individuals with infantile‐onset epilepsy who had epilepsy gene panel testing. We reviewed records, updated variant classifications, and compared phenotypic features. Wilcoxon rank‐sum tests and χ2 or Fisher's exact tests were performed for between‐cohort comparisons. Results We identified 137 individuals with CDD (110 females, 80.3%; median age at last follow‐up 3 year 11 months) and 313 individuals with infantile‐onset epilepsies (156 females, 49.8%; median age at last follow‐up 5 years 2 months; 35% with genetic diagnosis). Features reported significantly more frequently in the CDD group than in the comparison cohort included developmental and epileptic encephalopathy (81% vs 66%), treatment‐resistant epilepsy (95% vs 71%), sequential seizures (46% vs 6%), epileptic spasms (66% vs 42%, with hypsarrhythmia in 30% vs 48%), regression (52% vs 29%), evolution to Lennox–Gastaut syndrome (23% vs 5%), diffuse hypotonia (72% vs 36%), stereotypies (69% vs 11%), paroxysmal movement disorders (29% vs 17%), cerebral visual impairment (94% vs 28%), and failure to thrive (38% vs 22%). Interpretation CDD, compared with other suspected or confirmed genetic epilepsies presenting in the first year of life, is more often characterized by a combination of treatment‐resistant epilepsy, developmental and epileptic encephalopathy, sequential seizures, spasms without hypsarrhythmia, diffuse hypotonia, paroxysmal movement disorders, cerebral visual impairment, and failure to thrive. Defining core phenotypic characteristics will improve precision diagnosis and treatment. CDKL5 deficiency disorder, compared to other infantile‐onset suspected or confirmed genetic epilepsies presenting in the first year of life is more often characterized by a combination of refractory seizures, seizures with multiple phases, diffuse hypotonia, cerebral visual impairment, and paroxysmal movement disorders. Defining core phenotypic characteristics of CDKL5 deficiency disorder will improve precision diagnosis and treatment. This original article is commented on by Kaufmann on pages 410–411 of this issue.