[High prevalence of specific language impairment in Robinson Crusoe Island. A possible founder effect].

BACKGROUND Specific language impairment (SLI) occurs in 2% to 8% of preschool children. Major and candidate genes are probably involved. Genetic drift is a cause for the presence of high frequencies of deleterious alíeles of a specific disease and the founder effect is one of its forms. Robinson Crusoe Island has 633 inhabitants and its actual population began with 8 families that repopulated the island at the end of XIXth century. AIM To assess the frequency of specific language impairment among children living in Robinson Crusoe Island. MATERIAL AND METHODS All 66 children aged between 3 and 9 years living in the island, were studied. Parents were interviewed and in children, non verbal intelligence, audiometric parameters, comprehension and expression of oral language were assessed. Extended genealogies were also performed. RESULTS Forty children had at least one parent that was descending of founder families. Among these, 35% had SLI. Eighth five percent of SLI affected children came from the same colonizer family. CONCLUSIONS The prevalence of SLI in Robinson Crusoe Island is higher than that reported in mainland Chile and abroad. This high prevalence, associated to a high frequency of consanguinity, supports the influence of genetic mechanisms in SLI transmission, based on a founder effect.