RESUMO
Background: The presence of major genes in the susceptibility of non syndromic cleft lip with or without cleft palate (CL/P) in Chile has been postulated, considering the high prevalence and familial aggregation of this condition. Aim: To study the familial recurrence of CL/P in Chile. Patients and methods: The recurrence risk of CL/P was studied in 217 extended pedigrees where 33 (15.2 percent) were multiplex (21 male and 12 female propositi). These multiplex extended pedigrees (with more than one affected individual) represented 75 nuclear pedigrees, constituted by 840 males and 803 females and are the basic information of this study. Results: A significantly higher frequency of affected males (4.15 percent) than affected females (2.27 percent) was observed, independent of the difference in number of propositi by sex. Even though no differences were observed between families where both parents were unaffected, compared to those with only one affected parent, a higher proportion of affected descendants was found when the affected propositi was the mother. In multiplex families, the recurrence risk, according to the genetic proximity to the proband, was 10.1, 3.6 and 3.3 percent respectively for first, second and third degree relatives. The figures were 1.5, 0.5 and 0.4 percent respectively, when adjusted to the 217 extended pedigrees. Considering that the risk for the general population in Chile is approximately 0.16 percent, it is 10.3, 3.2 and 2.6 times higher among affected families. Conclusions: The high heritability of CL/P and the risk encountered for the Chilean population supports the hypothesis of major genes involved in its susceptibility