KCTD7‐related progressive myoclonic epilepsy: Report of 42 cases and review of literature

Abstract

ObjectiveKCTD7‐related progressive myoclonic epilepsy (PME) is a rare autosomal‐recessive disorder. This study aimed to describe the clinical details and genetic variants in a large international cohort.MethodsFamilies with molecularly confirmed diagnoses of KCTD7‐related PME were identified through international collaboration. Furthermore, a systematic review was done to identify previously reported cases. Salient demographic, epilepsy, treatment, genetic testing, electroencephalographic (EEG), and imaging‐related variables were collected and summarized.ResultsForty‐two patients (36 families) were included. The median age at first seizure was 14 months (interquartile range = 11.75–22.5). Myoclonic seizures were frequently the first seizure type noted (n = 18, 43.9%). EEG and brain magnetic resonance imaging findings were variable. Many patients exhibited delayed development with subsequent progressive regression (n = 16, 38.1%). Twenty‐one cases with genetic testing available (55%) had previously reported variants in KCTD7, and 17 cases (45%) had novel variants in KCTD7 gene. Six patients died in the cohort (age range = 1.5–21 years). The systematic review identified 23 eligible studies and further identified 59 previously reported cases of KCTD7‐related disorders from the literature. The phenotype for the majority of the reported cases was consistent with a PME (n = 52, 88%). Other reported phenotypes in the literature included opsoclonus myoclonus ataxia syndrome (n = 2), myoclonus dystonia (n = 2), and neuronal ceroid lipofuscinosis (n = 3). Eight published cases died over time (14%, age range = 3–18 years).SignificanceThis study cohort and systematic review consolidated the phenotypic spectrum and natural history of KCTD7‐related disorders. Early onset drug‐resistant epilepsy, relentless neuroregression, and severe neurological sequalae were common. Better understanding of the natural history may help future clinical trials.