[Polydactyly: a genetic epidemiological study in Santiago, Chile].

The aim of this work was to study the prevalence at birth and family aggregation of polydactyly in Chile. We studied 125,652 newborns between 1969 and 1991. The prevalence was 1,329 for each 1,000 live newborns and higher in males than in females. Familial recurrence was 22.5% and gene penetrance was estimated as 0.5 for the postaxial-A type and 0.3 for the postaxial-B type. Gene penetrance for postaxial-B type was higher in males. Estimation of gene frequencies and mutation rates gave the highest values for postaxial-B polydactyly.