Speech-Sound Disorder

Clinical Features

Speech-sound disorder (SSD) is a complex behavioral disorder characterized by speech-sound production errors associated with deficits in articulation, phonologic processes, and cognitive linguistic processes. SSD is prevalent in childhood and is comorbid with disorders of language, spelling, and reading disability, or dyslexia. SSD has a high prevalence in preschool children, estimated at approximately 16% at age 3 years, with 3.8% of children continuing to present with speech delay at age 6 years (Shriberg et al., 1999). More than half of these children encounter later academic difficulties in language, reading, and spelling.

Inheritance

Evidence that susceptibility to SSD is genetic is provided by twin studies, familial aggregation studies, and segregation and linkage analyses (review by Stein et al., 2004).

Mapping

Pennington and Lefly (2001) and Tunick and Pennington (2002) proposed that early developmental problems in spoken language predict the later emergence of dyslexia in children from high-risk families. Nopola-Hemmi et al. (2001) analyzed a large Finnish pedigree segregating for developmental dyslexia in an autosomal dominant fashion and found linkage to the pericentromeric region of chromosome 3 (DYX5; 606896). On the basis of the hypothesis that SSD and dyslexia share genetic determinants, Stein et al. (2004) genotyped markers in the dyslexia candidate region on chromosome 3 to determine whether linkage would be observed in families ascertained through a proband with SSD. They studied 77 such families. The quantitative scores measured several processes underlying speech-sound production, including phonologic memory, phonologic representation, articulation, receptive and expressive vocabulary, and reading, decoding, and comprehension skills. In multipoint analyses, measures of phonologic memory demonstrated strongest linkage to the chromosome 3 pericentromeric region. The results suggested that domains common to SSD and dyslexia are pleiotropically influenced by a putative quantitative trait locus on chromosome 3.