Identification of novel CDH23 variants linked to hearing loss in a Chinese family: A case report

Abstract

Rationale: Deafness is associated with both environmental and genetic factors, with hereditary deafness often caused by mutations in deafness-related genes. Identifying and analyzing deafness-related genes will aid in early diagnosis and pave the way for treating inherited deafness through gene therapy in the future.

Patient concerns: A 15-month-old girl underwent audiological examination at the outpatient clinic of the hospital due to hearing loss and her brother was diagnosed with profound bilateral sensorineural hearing loss at the age of 3.

Diagnoses: The diagnosis was determined as extremely severe sensorineural hearing loss caused by genetic factors.

Interventions: Clinical data of the patient were collected, and peripheral blood samples were obtained from both the patient and her family members for DNA extraction and sequencing.

Outcomes: By utilizing targeted capture next-generation sequencing to further screen for deafness-related genes, 2 novel variants in CDH23 were identified as the causative factors for the patient's deafness.

Lessons: This study identified 2 novel heterozygous mutations in a Chinese family. Both the proband and her sibling have non-syndromic hearing loss (NSHL) and carry distinct heterozygous mutations of cadherin-like 23 (CDH23). One mutation, CDH23:c.2651 A>G, originated from their mother and paternal family, affecting the exon23 domain of CDH23. The other mutation, CDH23:c.2113 G>T, was inherited from their paternal grandmother, impacting the exon19 domain of CDH23. These 2 novel mutations likely cause NSHL by affecting protein function. This finding suggests that identifying 2 novel mutations in CDH23 contributes to the genetic basis of NSHL.

Figure 1.

Pedigree of the family with hearing loss due to a pathogenic variant. Affected individuals are depicted in black, with the proband indicated by an arrow. The black “+” represents the c.2113 G>T (p.Gly705Cys) mutation, while the red “+” represents the c.2651 A>G (p.Asn884Ser) mutation.

Figure 2.

Pure-tone audiometry results of proband and her sibling.

Figure 3.

Protein alignment of CDH23 in different species, which shows the conservation of residue p. Asn884Ser and p. Gly705Cys.

Figure 4.

Sanger sequencing result of c.2113 G>T (p. Gly705Cys) and c.2651 A>G (p. Asn884Ser) variants in CDH23.

Figure 5.

The structures of c.2113 G>T (p.Gly705Cys) and c.2651 A>G (p. Asn884Ser) variants in CDH23.