Medical genetics for the otorhinolaryngologist.

Genetic disorders involving the ear, nose and throat can be looked at in essentially the same way that one would view other genetic problems. It is important to differentiate genetic disorders from those due to environmental influences. This may be difficult on clinical grounds, since similar clinical features may be produced by different environmental factors or by different genes or groups of genes. When the cause of the disorder can be established, the risks involved in a family having further offspring usually can be determined reasonably readily. In the uncharacterized situations, empiric risk figures are employed. Abnormalities of genetic origin fall into one of three main groupings: chromosomal abnormalities, single gene mutations or polygenic inheritance. These situations are discussed and examples are given.