Background:
Genetic deficits cause 80% of congenital prelingual hearing loss. Some 80% of these cases are nonsyndromic and most follow an autosomal recessive pattern of inheritance. More than 80 genes have so far been identified as pathogenic. In this study, we focus on a recently mapped gene, LOXHD1, whose mutated form causes DFNB77 hearing loss, and find a new variant.

Case report:
This is a case study of a 7-year-old male who was admitted to our audiology department with progressive hearing impairment. Pure tone audiometry showed bilateral symmetric hearing impairment, especially at mid to high frequencies. Acoustic immittance tests were normal, but transient evoked otoacoustic emissions and auditory brainstem responses were abnormal for both ears. After physical, clinical, and imaging evaluations, the patient and his parents were genetically tested. Genetic screening showed LOXHD1 hearing loss with a novel combination of alleles, the first such case diagnosed in Greece. The patient now has hearing aids and is being regularly monitored.

Conclusions:
Autosomal recessive nonsyndromic hearing loss (ARNSHL), including DFNB77, is the most common sensory deficit in children. Our work describes the first LOXHD1 hearing loss case diagnosed in Greece and adds a novel pathogenic variant to the list of pathogenic LOXHD1 gene variants.