[Practical medico-genetic counseling for congenital and early loss of hearing in children].

Current knowledge of hereditary loss of hearing provides a basis for effective diagnosis and prevention of hearing disorder. There is a little doubt of the necessity of medico-genetic counseling (MGC) for families facing this with problem. New molecular methods for the detection of its causes give hope to many couples in terms of rational family planning. We had an opportunity to compare results of MGC for the loss of hearing using these methods and without DNA-diagnosis and would like to familiarize clinicians with our experience in counseling such families. The majority of the children in whom hereditary loss of hearing was due to 35delG mutation in the connexin gene 26 (Cx26) had no hearing problems in the family history and their parents had normal hearing abilities. Hereditary loss of hearing in such patients can be diagnosed only by DNA analysis. We describe more complex variants of hearing disdetection in the counseled families and illustrate the importance of whole gene Cx26 analysis in 10 of them by the DNA sequencing technique. Testing for a single mutation is insufficient for correct diagnosis. Identification of such families provides data for the extension of the group at risk of congenital loss of hearing. Effective diagnosis can be achieved by improved molecular analysis and close cooperation between specialists conducting prospective and retrospective family counseling.