SMC1A epilepsy syndrome: clinical data from a large international cohort.

SMC1A epilepsy syndrome or developmental and epileptic encephalopathy-85 with or without midline brain defects (DEE85, OMIM #301044) is an X-linked neurologic disorder associated with mutations of the SMC1A gene, which is also responsible for about 5% of patients affected by Cornelia de Lange syndrome spectrum (CdLS). Only described in female patients, SMC1A epilepsy syndrome is characterized by the onset of severe refractory epileptic seizures in the first year of life, global developmental delay, a variable degree of intellectual disability, and dysmorphic facial features not typical of CdLS. This was a descriptive observational study for the largest international cohort with this specific disorder. The main goal of this study was to improve the knowledge of the natural history of this phenotype with particular attention to the psychomotor development and the epilepsy data. The analyzed cohort shows normal prenatal growth with the subsequent development of postnatal microcephaly. The incidence of neonatal problems (seizures and respiratory compromise) is considerable (51.4%). There is a significant prevalence of central nervous system (20%) and cardiovascular malformations (20%). Motor skills are generally delayed. The presence of drug-resistant epilepsy is confirmed; the therapeutic role of a ketogenic diet is still uncertain. The significant regression of previously acquired skills following the onset of seizures has been observed. Facial dysmorphisms are variable and no patient shows a classic CdLS phenotype. To sum up, SMC1A variants caused drug-resistant epilepsy in these patients, more than two-thirds of whom were shown to progress to developmental and epileptic encephalopathy. The SMC1A gene variants are all different from each other (apart from a couple of monozygotic twins), demonstrating the absence of a mutational hotspot in the SMC1A gene. Owing to the absence of phenotypic specificity, whole-exome sequencing is currently the diagnostic gold standard.

Comprehensive review and expanding the genetic landscape of Cornelia-de-Lange spectrum: insights from novel mutations and skin biopsy in exome-negative cases.

BACKGROUND: Cornelia de Lange Syndrome (CdLS) is a rare genetic disorder characterized by a range of physical, cognitive, and behavioral abnormalities. This study aimed to perform a comprehensive review of the literature on CdLS and investigate two cases of CdLS with distinct phenotypes that underwent WES to aid in their diagnosis. METHODS: We conducted a comprehensive review of the literature on CdLS along with performing whole-exome sequencing on two CdLS patients with distinct phenotypes, followed by Sanger sequencing validation and in-silico analysis. RESULTS: The first case exhibited a classic CdLS phenotype, but the initial WES analysis of blood-derived DNA failed to identify any mutations in CdLS-related genes. However, a subsequent WES analysis of skin-derived DNA revealed a novel heterozygous mutation in the NIPBL gene (NM_133433.4:c.6534_6535del, p.Met2178Ilefs*8). The second case was presented with a non-classic CdLS phenotype, and WES analysis of blood-derived DNA identified a heterozygous missense variant in the SMC1A gene (NM_006306.4:c.2320G>A, p.Asp774Asn). CONCLUSIONS: The study shows the importance of considering mosaicism in classic CdLS cases and the value of WES for identifying genetic defects. These findings contribute to our understanding of CdLS genetics and underscore the need for comprehensive genetic testing to enhance the diagnosis and management of CdLS patients.

Clinical characteristics and gene analysis of SMC1A gene related disorders / 中华神经科杂志

Objective:To analyze the clinical characteristics and genetic features of SMC1A gene related disorders. Methods:The data of 5 children with SMC1A gene variants were collected from Children′s Hospital of Fudan University from February 2018 to January 2022. The clinical features, electroencephalogram (EEG), brain imaging and gene testing results were summarized. Results:Among the 5 patients, 4 are females and 1 is male. Two female cases are siblings. One boy had dysmorphic features, consisting of bilateral ptosis, synophrys, a short nose and upturned nasal tip. He also had patent foramen ovale plus atrial septal defect, unilateral cryptorchidism and microcephaly. Three cases had microcephaly. Two girls had patent foramen ovale, and 2 girls had microcephaly. Four cases had epilepsy, and age at seizure onset ranged from 2 to 52 months. Multiple seizure types were observed, including bilateral tonic clonic seizures in 2 patients, and focal seizures in 3 patients. The seizures in 3 cases were in cluster. All patients had developmental delay, including 1 patient with mild and 4 patients with moderate to severe developmental delay. Three patients had slow background activity in EEG. Interictal EEG showed abnormal discharges in 4 patients, including focal discharges in 3 cases and generalized discharges in 1 case. Brain magnetic resonance imaging was normal in 3 patients and showed mild cortical thickening in 1 case. All cases harbored 4 SMC1A gene variants, including 2 missense variants and 2 frameshift variants (c.580_587del, c.2699delG, c.3362G>A, c.1486C>T). Three cases harbored heterozygous SMC1A variants and 2 cases carried somatic mosaic SMC1A variants with 17.5% and 88.1% mosaicism in peripheral blood. The follow-up lasted for 3 months to 4 years. The epilepsy was refractory in 2 cases. During the follow-up, all cases had very slow developmental progress or developmental retardation. All cases had different levels of growth retardation. The scores of Cornelia de Lange syndrome (CdLS) phenotypes in 5 cases were 2-6. One case had the combined phenotypes of atypical CdLS and developmental epileptic encephalopathy (DEE). The phenotype was atypical CdLS in 1 case and DEE in 1 case. The phenotypes of 2 cases with SMC1A missense variants were mild, manifesting as non-refractory epilepsy and moderate to severe developmental delay. Conclusions:All of cases with SMC1A gene variants have developmental delay. Most of the patients have clusters of seizures and some dysmorphisms. The phenotypes of SMC1A gene related disorders are diverse. Except CdLS and DEE, there are some patients with mild phenotype due to missense variants of SMC1A gene.

Cornelia de Lange syndrome with recurrent seizures and SMC1A gene c. 2923C > T mutation: a case report and literature review / 中华实用儿科临床杂志

Objective:To explore the characteristics, clinical manifestations and gene mutation types of Cornelia de Lange syndrome (CdLs), and to improve the understanding of the disease.Methods:Clinical data and gene test results of a pediatric case of CdLs diagnosed in the First Affiliated Hospital of Xinxiang Medical University in August 2019 were analyzed retrospectively.Results:A female patient with 2 years and 8 months old presented a special appearance with a low and flat nose, a wide eye distance, audition ears, a downward inclination of the mouth corner, a high arch of the jaw and a small jaw deformity, who had recurrent seizures, speech and mental retardation.The result of gene test showed the mutation of SMC1A gene c. 2923C > T, and thus the patient was diagnosed as type 2 CdLs. Conclusions:CdLs is a rare genetic metabolic disease with special facial features and physical signs.There is only one case of CdLs with gene mutation of SMC1A in China through literature review.The mutation of SMC1A gene c. 2923C>T in CdLs cases has not been reported at home and abroad, which expands the variation spectrum of the SMC1A gene.