The aims are to co-ordinate research on genetic deafness and establish research and clinical data banks, combining clinical in-depth family and phenotypic studies with basic molecular genetic and gene mapping methods.
The loss of hearing results in social isolation and it imposes a severe economic and social burden on those affected. Hereditary factors account for a large portion not only of congenital and early onset deafness, but also of progressive bilateral hearing loss. Identification of probands having similar phenotype is difficult because many genes are involved and different mutations can cause similar phenotypes. Progress in this field are also difficult for paucity of clinical criteria and the vagueness of definitions used by the different professionals involveded. Genetic heterogeneity among subjects greatly complicates the task of mapping genes by linkage analysis; therefore it is essential to have families which have been meticulously characterised clinically. For syndromal hearing loss, the main obstacle to obtain a homogeneous series of families is the difficulty to find a sufficiently large number of subjects affected by the same disorder, since usually, these conditions are rare. For non-syndromal hearing loss, the research strategy must be designed to accomodate genetic heterogeneity, and careful clinical documentation, using uniform protocols and definitions, distinguishing subgroups. Extensive collaboration is usually necessary. This project is carried out dividing centres members into study subgroups, which although interactive and in connection with one another, have the task of developing a particular line of research. The subgroups are: 1) Study group on terminology, definitions and hearing assessment, 2) Study group on epidemiology of genetic hearing impairment, 3) Study group on vestibular involvement, 4a) Study group on cranio-facial malformation and hearing impairment, 4b) Study group on otological malformations and associated surgical problem, 5) Study group on identification of genes. The groups will co-operate on: a) establishing common terminology and definitions; b) classification of families based on the characteristics of hearing impairment, vestibular function, inner ear malformations and other phenotypic criteria, and genetic transmission; c) promotion of the co-operation between clinicians and molecular geneticists for identification of genes and products causing hearing impairment d) edition of an Infoletter to spread information on work on progress and publication of a bulletin to inform families and the public on this issue; e) investigate the genotype-phenotype correlation; f) provide European epidemiological data about genetic hearing impairment and the frequency of the occurrence of mapped genes, and sex distribution; g) investigate relationship between environment and genetic disorders; h) provide European research and clinical data bank and a list of researchers in this field in order to facilitate diagnosis and expert medical counselling. The coordinated action of clinicians and geneticists will favour and speed the discovery of genes responsible of hearing impairment as well as lead to better understanding of hearing physiology. Data will also be useful in programming medical costs and services for diagnosis, care and rehabilitation.