Genetic analysis of a child with Charlevoix-Saguenay spastic ataxia due to variant of SACS gene / 中华医学遗传学杂志

OBJECTIVE@#To explore the clinical feature and genetic variant of a child with autosomal recessive Charlevoix-Saguenay type spastic ataxia (ARSACS).@*METHODS@#Clinical data of a child who was admitted to the West China Second Hospital of Sichuan University on April 30, 2021 was collected. Whole exome sequencing (WES) was carried out for the child and his parents. Candidate variants were verified by Sanger sequencing and bioinformatic analysis based on the guidelines from the American College of Medical Genetics and Genomics (ACMG).@*RESULTS@#The child, a 3-year-and-3-month-old female, had a complain of "walking instability for over a year". Physical and laboratory examination revealed progressive and aggravated gait instability, increased muscle tone of the right limbs, peripheral neuropathy of the lower limbs, and thickening of retinal nerve fiber layer. The results of WES revealed that she has harbored a maternally derived heterozygous deletion of exons 1 to 10 of the SACS gene, in addition with a de novo heterozygous c.3328dupA variant in exon 10 of the SACS gene. Based on the ACMG guidelines, the exons 1-10 deletion was rated as likely pathogenic (PVS1+PM2_Supporting), and the c.3328dupA was rated as a pathogenic variant (PVS1_Strong+PS2+PM2_Supporting). Neither variant was recorded in the human population databases.@*CONCLUSION@#The c.3328dupA variant and the deletion of exons 1-10 of the SACS gene probably underlay the ARSACS in this patient.

De novo variant of CSNK2B causes Poirier-Bienvenu neurodevelopmental syndrome: two case report / 中华医学遗传学杂志

OBJECTIVE@#To analyze the clinical characteristics and CSNK2B gene variant of 2 children with Poirier-Bienvenu neurodevelopmental syndrome, and to identify the possible pathogenic causes and provide evidence for clinical diagnosis.@*METHODS@#Two children with Poirier-Bienvenu neurodevelopmental syndrome were selected from West China Second University Hospital, Sichuan University. The clinical manifestations, laboratory examination and CSNK2B gene variant were analyzed.@*RESULTS@#The main manifestations of 2 children were epilepsy, motor or intellectual retardation. Whole exon sequencing showed that CSNK2B gene c. 291+4A>T heterozygous splicing variant was found in case one, and CSNK2B copy number variation(CNV) was lost in case two. Case one received no special treatment, followed up for 8+ months, seizures and motor development were improved; case two had recurrent seizures for 9+ years, and received levetiracetam and clonazepam antiepileptic treatment. No seizures have occurred for 2 years now, and a large number of epileptic discharges can still be seen in video electroencephalogram (VEEG) with slightly backward intelligence and language development.@*CONCLUSION@#Our study further proves that the pathogenic variant of CSNK2B is related to epilepsy with developmental disorder, and enrich is the CSNK2B gene variant spectrum. The pathogenesis of CSNK2B has great clinical heterogeneity, with great difference in severity of nervous system injury and different prognosis, and agenesis of corpus callosum may be one of its clinical phenotypes.

Analysis of a case with Xia-Gibbs syndrome due to variant of AHDC1 gene / 中华医学遗传学杂志

OBJECTIVE@#To analyze the clinical and genetic characteristics of a child featuring Xia-Gibbs syndrome.@*METHODS@#Whole exome sequencing was carried out for the child.@*RESULTS@#The patient has presented with developmental delay, hypotonia, strabismus and snoring. Cranial MRI revealed hypomyelination, while the EEGs were normal. Genetic testing revealed a de novo variant of the AHDC1 gene, namely c.730delA (p.Ile244Serfs*16), which was classified as pathogenic (PVS1+PS2+PM2). Together with 60 cases from the literature, individuals harboring a AHDC1 variant commonly have delayed motor milestones, speech delay, facial dysmorphism and hypotonia. Dysgenesis of corpus callosum is also common. In total 47 AHDC1 variants have been reported, among which truncating variants were the most common type.@*CONCLUSION@#The c.730delA (p.Ile244Serfs*16) variant of the AHDC1 gene probably underlay the Xia-Gibbs syndrome in this patient. Above finding has provided a basis for the clinical diagnosis.

Analysis of clinical features and ZBTB18 gene variant in a child with autosomal dominant mental disorder type 22 / 中华医学遗传学杂志

OBJECTIVE@#To analyze the clinical characteristics and ZBTB18 gene variant in a child with epilepsy and global developmental delay.@*METHODS@#Clinical data and laboratory examination of the patient were reviewed. Whole exome sequencing (WES) was also carried out for the family trio.@*RESULTS@#The main manifestations of the child included global developmental delay, short stature, epileptic seizures. EEG revealed frequent occurrence of sharp (slow) waves in the right central region during sleeping, with sharp waves occasionally seen in the frontal and right posterior temporal regions. Cranial MRI has shown no obvious abnormality. WES has identified a de novo pathogenic variant in the ZBTB18 gene [NM_205768.3: exon 2: c.1282_1283del (p.Phe428Leufs*72)]. Based on the guidelines from American College of Medical Genetics and Genomics (ACMG), the variant was classified as pathogenic (PS2+PVS1_Moderate+PM2_Supporting). Following treatment with levetiracetam and rehabilitation, the seizures have been controlled for nearly half a year, with improvement of the psychomotor and language development. So far 28 children have been discovered with ZBTB18 gene mutations, and there was a significant difference in the clinical phenotypes of motor retardation, language retardation and epilepsy between those harboring frameshift/nonsense mutations and missense mutations.@*CONCLUSION@#The c.1282_1283del (p.Phe428leufs *72) variant of the ZBTB18 probably underlay the autosomal dominant mental disorder type 22 in this child. Compared with missense mutations, frameshift/nonsense mutations may predispose more to motor retardation, delayed language development and epilepsy.