A TBC1D24 gene variant coincides with STRC compound heterozygosity in a family with hearing loss: a case report

Abstract

BackgroundHearing loss is a common inborn neurosensory condition. Hearing loss is very heterogeneous, and while screening programs exist for children, adolescents and adults with late-onset hearing loss often do not get referrals to geneticists.ObjectiveTo diagnose the cause of hearing impairment in two related late-onset hearing loss patients—father and son—on a molecular level. Both underwent audiological examinations, and both had moderate hearing loss.Case presentation.We used massive parallel sequencing, Sanger sequencing, MLPA, and standard audiological methods. We identified an inherited autosomal dominant likely causative variant in the TBC1D24 gene of both patients. They did not show any other TBC1D24 spectrum-related symptoms. Furthermore, the younger patient was found to be compound heterozygous for two variants in STRC gene.ConclusionsOnly a few dozen TBC1D24 hearing loss patients have been reported. On the contrary, STRC is a common hearing loss cause. We speculate that in the younger patient, the phenotype is caused by a combination of effects of both genes. The older patient’s phenotype is more likely caused only by the TBC1D24 variant. We believe that more attention should be paid to adolescent and adult-onset hearing loss patients, and more frequent referrals to geneticists are warranted.