MedGen

Stuttering is a disorder of the flow of speech characterized by involuntary repetitions or prolongations of sounds or syllables, and by interruptions of speech known as blocks (summary by Raza et al., 2010). Stuttering typically arises in young children, where it affects at least 15% of those in age range 4 to 6 years (Bloodstein, 1995). Stuttering usually resolves spontaneously before adolescence, leading to a population prevalence of 1 to 2% among adults. Stuttering beyond childhood is characterized by a significant bias towards males, with males outnumbering females by a ratio of 3:1 to 5:1 (Yairi et al., 1996). Genetic Heterogeneity of Familial Persistent Stuttering Also see STUT2 (609261), mapped to chromosome 12q24; STUT3 (614655), mapped to chromosome 3q; and STUT4 (614668) mapped to chromosome 16q. [from OMIM]

X-linked autism-6 is a neurodevelopmental disorder that affects only males. Some patients may respond favorably to carnitine supplementation (summary by Ziats et al., 2015). Autism, the prototypic pervasive developmental disorder (PDD), is usually apparent by 3 years of age. It is characterized by a triad of limited or absent verbal communication, a lack of reciprocal social interaction or responsiveness, and restricted, stereotypic, and ritualized patterns of interests and behavior (Bailey et al., 1996; Risch et al., 1999). 'Autism spectrum disorder,' sometimes referred to as ASD, is a broader phenotype encompassing the less severe disorders Asperger syndrome (see ASPG1; 608638) and pervasive developmental disorder, not otherwise specified (PDD-NOS). 'Broad autism phenotype' includes individuals with some symptoms of autism, but who do not meet the full criteria for autism or other disorders. Mental retardation coexists in approximately two-thirds of individuals with ASD, except for Asperger syndrome, in which mental retardation is conspicuously absent (Jones et al., 2008). Genetic studies in autism often include family members with these less stringent diagnoses (Schellenberg et al., 2006). For a discussion of heterogeneity of autism, see 209850. [from OMIM]