Heart problems and deafness: Are they more common than supposed?

Abstract

In 2005, the World Health Organization (WHO) estimated that 12.5 million people worldwide are affected by bilateral profound hearing loss. Congenital hearing loss is the hereditary sensorial defect most commonly observed in newborns; it affects 1.12 per 1000 children. If we also consider acquired forms and late-onset forms of hearing loss, prevalence grows to 1.33 per 1000 children. In Italy the overall prevalence is 0.78 per 1000 for males and 0.69 per 1000 for females (1). Fifty percent of sensorineural deafness is due to genetic causes, most of which are inherited in an autosomal recessive manner. Genetic deafness is very heterogeneous and can occur in non-syndromic form (70% of cases) or in syndromic form (30% of cases). Several syndromes are associated with deafness, heart anomalies and other diseases: Charge syndrome, Leopard syndrome, Fabry syndrome, Refsum syndrome, SALL4 syndrome and Mobius syndrome. Until recently only one syndrome in which deafness and heart problems are the sole features has been described – Jervell and Lange-Nielsen syndrome (J-LNS). This condition, if not timely discovered and treated, may culminate in sudden death. However, in December 2010, Nature Neuroscience published an article about a new channelopathy termed SANDD syndrome, characterized by sinoatrial node dysfunction and deafness (2). These recent data underline the importance of a cardiac investigation in cases of suspected genetic deafness of unknown cause. It is probable that in the future other syndromes involving both the heart and the hearing system will be found. We have to consider that many of the causative genes of deafness have not yet been identifi ed. Furthermore, genes involved in hearing impairment encode proteins of different classes, such as cell adhesion and cytoskeleton proteins, transcription factors, extracellular matrix components, membrane