Hearing loss (HL) is the most common sensory impairment, and it is characterized by a high clinical/genetic heterogeneity. Here we report the identification of dual molecular diagnoses (i.e., mutations at two loci that lead to the expression of two Mendelian conditions) in a series of families affected by non-syndromic and syndromic HL. Eighty-two patients who displayed HL as a major clinical feature have been recruited during the last year. After an accurate clinical evaluation, individuals have been analyzed through whole-exome sequencing (WES). This protocol led to the identification of seven families characterized by the presence of a dual diagnosis. In particular, based on the clinical and genetic findings, patients have been classified into two groups: (a) patients with HL and distinct phenotypes not fitting in a known syndrome due to mutations at two loci (e.g., HL in association with Marfan syndrome) and (b) patients with two genes involved in HL phenotype (e.g., TMPRSS3 and MYH14). These data highlight for the first time the high prevalence of dual molecular diagnoses in HL patients and suggest that they should be considered especially for those cases that depart from the expected clinical manifestation or those characterized by a significant intra-familiar variability.
