Supervisors info:
Κοσμά Κωσταντίνα, Υποψήφιος Διδάκτωρ, Ιατρική Σχολή, ΕΚΠΑ
Μακρυθανάσης Περικλής, Επίκουρος Καθηγητής, Ιατρική Σχολή, ΕΚΠΑ
Συνοδινού-Traeger Ιωάννα, Καθηγήτρια, Ιατρική Σχολή, ΕΚΠΑ
Summary:
BACKGROUND: The sense of hearing plays a very important role in speech development, in the educational process, in socialization and in the normal psychomotor development of a child. However, hearing loss constitutes the fourth most common cause of disability worldwide. To date, about 20% of the population lives with hearing loss, while 34 million children worldwide experience some degree of hearing loss. The etiology of hearing loss varies, yet about 60% of congenital hearing loss cases are due to genetic causes. The diagnosis and management of pediatric hearing loss have undergone dramatic changes over the past 30 years. The developments in the field of medicine and the breakthrough in new technologies, such as the Next generation sequencing allow the early diagnosis of hearing loss with the aim of providing appropriate genetic counseling that will assure the best possible quality of life for the patient and his family. AIM: Understanding the function of hearing, identifying the types of hearing loss and analyzing the etiological factors that lead to hearing loss, focusing on the syndromic cases of hearing loss that occur most frequently in the general population and cause serious consequences. The identification of the available methods of genetic analysis and the importance of early and valid diagnosis in the outcome of patient’s health. METHODOLOGY: This is a literature search / review study for which Google, Pubmed and GeneReviews were used as the main information search engines. Information was obtained from official websites, such as: https://www.omim.org/, https://www.ncbi.nlm.nih.gov/ and for the search of articles were studied electronic journals of scientific content, such as: Orphanet Journal of Rare Diseases, American Journal of Medical Genetics, International Journal of Pediatric Otorhinolaryngology, Elsevier, Clinical Genetics, International Journal of Molecular Sciences. RESULTS: Clinically significant hearing loss occurs in 1-3 per 1000 births. Hearing loss is classified into three types: (1) Sensorineural hearing loss, (2) Conductive and (3) Mixed hearing loss. To this day we know of more than 400 syndromes that cause hearing problems, such as the CHARGE, Treacher Collins, Usher, Stickler and Pendred syndromes, which account for 30% of hearing-impaired genetic causes. On the other hand, more than 100 genes have been associated with the occurrence of hearing loss that do not correlate with a syndrome, such as the non-syndromic autosomal recessive hearing loss DFNB4 and DFNB1A and constitute 70% of the cases. The genetic factors responsible for hearing loss are highly heterogeneous, however the application of early genetic diagnostics, through DNA analysis using methods such as Sanger sequencing and New generation sequencing, is possible in most cases and is necessary as it provides prognostic information and acts as a pillar for providing accurate and personalized genetic counseling. CONCLUSIONS: Despite the high frequency of hearing disorders in the population and the advances made in the fields of medicine and biology, as well as the technological progress of recent years, there are still unknown genetic sites and unclear pathogenetic mechanisms. All this, in combination with the great phenotypic and genotypic heterogeneity that characterize the cases of genetic hearing loss, emphasize the need for further studies that will enrich the knowledge of the scientific community and will assist in the development of methods aiming at the provision of holistic and individualized care to patiens and their families.
Keywords:
Hereditary hearing loss, Syndromic hearing loss, Non-syndromic hearing loss, Genetic testing
