Late-onset cluster seizures caused by a truncation variation in SMC1A gene: a case report and literature review / 中华神经科杂志

ABSTRACT

Objective:To summarize the clinical phenotype and genotypic characteristics of children with truncation variation in SMC1A gene. Methods:The clinical data of a child with late-onset cluster seizures caused by truncation variation in SMC1A gene diagnosed in February 2021 in Children′s Hospital Affiliated to Zhengzhou University were collected. The relevant literature was reviewed to summarize the clinical characteristics. Results:The proband was a 5-year-old girl, presenting with first seizure at the age of 5 and cluster seizures. She had poor response to multiple antiepileptic drugs, and had normal neurodevelopment before seizures. Whole exome sequencing results revealed a spontaneous heterozygous nonsense variation c.55C>T in SMC1A gene, causing a nonsense variant in the amino acid sequence p.Gln19Ter(p.Gln19 *), which has not been reported. There were a total of 14 relevant literatures, and there were in total 32 cases with truncation variation in SMC1A gene including this case. All children were female and 30 children had early-onset intractable epilepsy, and first seizure median age was 5 months (range 4 weeks to 40 months); 78.1% (25/32) of them had cluster seizures; 93.8% (30/32) had mental retardation; Cornelia de Lange syndrome clinical score in 68.8% (22/32) of them was≥4. The truncation variations in SMC1A gene of 31 children were de novo, and there were 16 children with frameshift variation (16/32), 12 children with nonsense variation [12/32; 3 children (9.4%, 3/32) with c.2923C>T], 4 children with splice variation (4/32). Conclusions:This study further expands the clinical phenotype and genotype of cases with truncation variation in SMC1A gene. Case presenting with female late-onset cluster seizures has not been reported in China, and genetic testing can be beneficial for early diagnosis of hereditary epilepsy and precision treatment.