Genetic aspects of idiopathic speech and language disorders.

At the outset of this article, we posed the question of whether or not the current evidence from genetic studies of DLD and stuttering indicate that it would be fruitful to conduct studies aimed at determining the gene location for each of these disorders. As we pointed out, because these are behavioral development disorders, phenotypic variations and changes in characteristics through the life span pose problems when attempting to determine who is and is not affected. Further, because these disorders can be either idiopathic or secondary to a variety of causes, any genetic study must rule out or take account of cases secondary to other factors. Few studies conducted thus far have taken these problems into account, and the results must be considered tentative. Given these reservations, the results certainly point to a genetic component in both disorders, although the data collected thus far on DLD suggest a mendelian form of transmission. If further more intensive studies continue to support this model for DLD, linkage studies on this disorder are likely to be productive.