Developmental stuttering is a common disorder of speech dissiliency that is characterized by excessive repetitions of sounds, syllables, and monosyllabic words, as well as sound prolongations and complete blockages of the vocal tract. About 60 million people are affected and it is more common between the age of 3 and 6, when children begin forming sentences and connecting thoughts verbally. There are three types of stuttering known as developmental stuttering, neurogenic stuttering, and psychogenic stuttering. The exact pathophysiology of developmental stuttering is unknown; however, various family and twin studies have repeatedly implicated heredity as a major factor in the etiology of stuttering. It is clear that the genetic influence is not in the form of an exact single gene effect such as autosomal recessive, autosomal dominant, or x-linked in all families; however, in all of the inheritance forms it is influenced by sex with higher occurrence in males than females at a ratio of 4:1 in older children and adults. Recently special genetic locus has been determined on several autosomal chromosomes related to developmental stuttering. In this report, the proband is a 20-year-old boy was referred to our clinic for premarriage genetic counseling; he has been affected since 3 years and now is under cure. three generation study of his family show 13 individuals are affected by stuttering. For the first it occurred in the proband's grandfather and after this time about all of affected cases has been seen in consanguineous marriages. Therefore, the genetical inheritance of stuttering is crystal clear in this family and autosomal recessive inheritance pattern is proposed. Totally in such families with repeated occur of stuttering, we cannot account it as a multifactorial disorder.

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