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

OBJECTIVE: KCTD7-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. METHODS: Families 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. RESULTS: Forty-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). SIGNIFICANCE: This 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.

Mitochondrial Complex I Deficiency Masquerading as Stroke-Like Episode Clinically and as Alexander Disease Radiologically Following Chicken Pox.

Mitochondrial disorders are a group of metabolic disorders with variable presentation and usually affect organs with high energy requirements like the brain, eye, and heart. Seventeen-month-old girl child presented with right hemiparesis and regression of milestones following chicken pox. Investigations showed elevated lactate, white matter signal changes in both periventricular and subcortical white matter with frontal predominance in the MRI of the brain, cardiomyopathy in the echocardiography, with complex I deficiency in respiratory enzyme assay in the muscle biopsy. A homozygous missense variant c.304C>T (p. Arg102Cys) in exon 5 of NDUFS8 gene (chr11:67800682C>T; NM_002496.4) was detected on whole exome sequencing with positive parental Sanger for the same gene. The child was started on a mitochondrial cocktail, ramipril, and frusemide. Mitochondrial complex deficiency should be considered in cases with stroke-like episodes, and predominant white matter involvement on imaging mimicking classical genetic leukodystrophy like Alexander disease.