Linkage of speech sound disorder to reading disability loci.

BACKGROUND Speech sound disorder (SSD) is a common childhood disorder characterized by developmentally inappropriate errors in speech production that greatly reduce intelligibility. SSD has been found to be associated with later reading disability (RD), and there is also evidence for both a cognitive and etiological overlap between the two disorders. The present study tested whether SSD is linked to replicated risk loci for RD. METHOD One hundred and eleven probands with SSD and their 76 siblings were tested with measures of speech, phonological memory (Nonword Repetition-NWR), and phonological awareness and genotyped for linkage markers on chromosomes 1p36, 6p22, and 15q21. Both single point and multipoint linkage were tested with multiple methods. RESULTS The speech and NWR phenotypes were linked to the RD loci on chromosomes 6 and 15, with suggestive results for the RD locus on chromosome 1. CONCLUSIONS It now appears that several RD loci are pleiotropic for SSD, extending the findings of Stein et al. (2004) for the RD locus on Chromosome 3.