Y-linked inheritance of non-syndromic hearing impairment in a large Chinese family.

H earing impairment is a common condition responsible for communication disorders affecting one in 1000 newborns. 2 A national poll by the China Association of the Handicapped in 1987 showed that 20.57 million people in the country were affected by auditory or speech disorders, accounting for 34% of the 60 million disabled or 1.58% of the total Chinese population (1.3 billion) (www.cdpf.org.cn). Hearing impairment is caused by environmental and hereditary factors. Environmental factors include perinatal infection, acoustic or cerebral trauma affecting the cochlea, and ototoxic drugs such as aminoglycoside antibiotics. 4 Genetic factors contribute to 50% of deafness cases including syndromic (30%) and non-syndromic (70%) hearing impairment. 5 Recent times have witnessed rapid progress in the field of genetic studies of hereditary hearing impairment, especially non-syndromic hearing impairment. Transmission of non-syndromic hearing impairment can be autosomal recessive (77%), autosomal dominant (22%), X-linked (1%), or matrilineal (mitochondrial inheritance, about 1%). More than 70 genetic loci have been characterised—that is, 37 for autosomal dominant, 34 for autosomal recessive, and 4 for X-linked forms of non-syndromic hearing impairment. A total of 36 genes (34 nuclear and two mitochondrial) have so far been identified. 7 To date, there has not been any report on Y-linked inheritance of hearing impairment. Recently, the Institute of Otolaryngology of the Chinese People’s Liberation Army (PLA) General Hospital has initiated a national network for collecting pedigrees of hereditary hearing loss. By collaborating with organisations for disabled people throughout China, many pedigrees with hereditary hearing loss have been identified and studied for deafness related genes. 9 This paper describes a highly unusual finding of an extended seven-generation Chinese pedigree with hearing impairment clearly vertically inherited through males. The inheritance characteristics in this family cannot be explained by the four transmission mechanisms mentioned above. A Y-linked inheritance pattern is thus proposed based upon the data of pedigree analysis, segregation analysis and linkage analysis with 382 autosomal microsatellite markers at the spacing of an average of 8.6 cM throughout the genome.