Identification of a novel mutation in the CHD7 gene in a patient with CHARGE syndrome

Suprameatal Cochlear Implantation in a CHARGE Patient With a Novel CHD7 Variant and KALLMANN Syndrome Phenotype: A Case Report

OBJECTIVE

We present the clinical findings, technique of the suprameatal cochlear implantation, postoperative auditory results, and genetic analysis of the CHD7 gene.

PATIENT

A 19-year-old Japanese woman was referred because of progressive hearing loss since early childhood. She had used verbal language for the main mode of communication until the age of 17. Examination revealed coloboma, heart defect, choanal atresia, genital hypoplasia, and deafness, which was diagnosed as CHARGE syndrome. Examination also revealed features of Kallmann syndrome.

INTERVENTIONS

Cochlear implantation was performed in the left ear at age 20. Targeted resequencing of the CHD7 gene was performed by next-generation sequencing.

RESULTS

Cochlear implantation was performed using a suprameatal approach (SMA) with cartilage protection because of a venous malformation of the temporal bone. The electrode introduced into the scala tympani through the cochleostomy could be fully inserted. The electrode was covered with cartilage to avoid contact with the skin of the external auditory canal. No intra- or postoperative complications have occurred up to 4 years postoperatively, and the patient uses verbal language again as the main mode of communication. A novel variant c.6405_6406delAG,p.(Ala2137Argfs*2) in CHD7 was identified by next-generation and Sanger sequencing analyses, resulting in a 2137-amino-acid truncated polypeptide. Parental genetic screening confirmed the sporadic origin of the mutation.

CONCLUSION

Cochlear implantation surgery using the SMA with cartilage protection technique appears to be a feasible and effective option for patients with ear anomalies that obstruct the usual approach. A novel frameshift variant c.6405_6406delAG,p.(Ala2137Argfs*2) in CHD7 was also identified in this patient.

Cerebellar vermis hypoplasia in CHARGE syndrome: clinical and molecular characterization of 18 unrelated Korean patients

CHARGE syndrome (OMIM 214800) is a rare autosomal-dominant congenital malformation syndrome that results from haploinsufficiency of the chromodomain helicase DNA-binding protein 7 (CHD7). We performed a phenotypic characterization and genetic analysis of CHD7 in 18 Korean patients with CHARGE syndrome. Eighteen unrelated Korean patients (10 females and 8 males; age range 0.0-19.6 years) with CHARGE syndrome were enrolled. Clinical data were collected by retrospective review of medical records. A serial analysis via sequencing and multiple ligation-dependent probe amplification of CHD7 was performed to determine the molecular genetic spectrum of the patients. The prevalence of cardinal symptoms was as follows: coloboma (13/18, 72.2%), heart defects (13/18, 72.2%), choanal atresia/stenosis (4/18, 22.2%), retarded growth (10/18, 55.6%), genital anomalies (15/18, 83.3%) and ear abnormalities (18/18, 100%). Five patients had cerebellar vermis hypoplasia (5/17, 29.4%) with no clinical symptoms or signs of cerebellar dysfunction. Furthermore, we identified genetic alterations in all 18 patients, including 10 novel mutations. Considering its frequency among patients with CHD7 mutations, cerebellar vermis hypoplasia may be a clinical diagnostic clue of CHARGE syndrome, although it is not included in the diagnostic criteria. And, the identification of CHD7 mutations may help the confirmative diagnosis.

Non-homologous end joining repair mechanism-mediated deletion of CHD7 gene in a patient with typical CHARGE syndrome

CHARGE syndrome MIM #214800 is an autosomal dominant syndrome involving multiple congenital malformations. Clinical symptoms include coloboma, heart defects, choanal atresia, retardation of growth or development, genital hypoplasia, and ear anomalies or deafness. Mutations in the chromodomain helicase DNA binding protein 7 (CHD7) gene have been found in 65-70% of CHARGE syndrome patients. Here, we describe a 16-month-old boy with typical CHARGE syndrome, who was referred for CHD7 gene analysis. Sequence analysis and multiplex ligation-dependent probe amplification were performed. A heterozygous 38,304-bp deletion encompassing exon 3 with a 4-bp insertion was identified. There were no Alu sequences adjacent to the breakpoints, and no sequence microhomology was observed at the junction. Therefore, this large deletion may have been mediated by non-homologous end joining. The mechanism of the deletion in the current case differs from the previously suggested mechanisms underlying large deletions or complex genomic rearrangements in the CHD7 gene, and this is the first report of CHD7 deletion by this mechanism worldwide.