Dyslexia affects 5–10% of school-age children [55] and is characterized by problems with word recognition and spelling. Linkage studies have revealed a number of chromosomal susceptibility loci for dyslexia (1p34-p36, 2p16-p15, 3p12-q12, 6p21, 6q13-q16, 11p15, 15q21, 18p11 and Xq27) [reviewed in 56]. Within and near these loci several genes have been studied using association analyses, resulting in a few candidate genes for dyslexia: dyslexia susceptibility 1 candidate 1 (DYX1C1; 15q21) [57], roundabout Drosophila homolog 1 (ROBO1; 3p12) [58] and doublecortin domain-containing protein 2 (DCDC2; 6p22.1) [59], but again the results are not conclusive and therefore the genetic aetiology of dyslexia is currently still unclear.
