Waardenburg syndrome (WS) is a common genetic cause of syndromic hearing loss, accounting for 2–5% of congenital cases. It is characterized by hearing impairment and pigmentation abnormalities in the skin, hair, and eyes. Seven genes are associated with WS: PAX3, MITF, EDNRB, EDN3, SOX10, KITLG, and SNAI2. This study investigates the genetic causes of WS in three familial cases. Whole-exome sequencing (WES) was performed to identify single nucleotide variants (SNVs). Copy number variants (CNVs) were analyzed from the WES raw data and through multiplex ligation-dependent probe amplification (MLPA). The study identified one pathogenic SNV and two novel CNVs, corresponding to type I and type II WS patterns in the three families. The SNV, a nonsense variant (c.1198C>T p.Arg400*), was found in MITF and segregated in the affected father. The two CNVs were a deletion of exon 5 in PAX3 in a family with two affected members and a large novel deletion comprising seven genes, including SOX10, in a family with three affected members. These findings confirmed a WS diagnosis through genetic testing. The study emphasizes the importance of integrating multiple genetic testing approaches for accurate and reliable diagnosis, highlighting their role in improving patient management and providing tailored genetic counseling.

Hereditary hearing loss stands as the most prevalent sensory disorder, with over 124 non-syndromic genes and approximately 400 syndromic forms of deafness identified in humans. The clinical presentation of these conditions spans a spectrum, ranging from mild to profound hearing loss. The aim of this study was to identify the genetic cause of hearing loss in a family and functionally validate a novel variant identified in the MYO6 gene. After Whole Exome Sequencing analysis, the variant c.2775G>C p.Arg925Ser in MYO6 was detected in a family with postlingual non-syndromic hearing loss. By protein modeling a change in the electrostatic charge of the single alpha helix domain surface was revealed. Through a knockdown phenotype rescue assay in zebrafish, the detrimental effects of the identified variant on the auditory system was determined. These findings underscore the significance of a comprehensive approach, integrating both in silico and in vivo strategies, to ascertain the pathogenicity of this candidate variant. Such an approach has demonstrated its effectiveness in achieving an accurate genetic diagnosis and in promoting a more profound comprehension of the mechanisms that underlie the pathophysiology of hearing.