Genetic characteristics of hemophilia A in Chile.

Abstract

A genetic and demographic study of 40 kindreds (113 cases) with hemophilia A, representing one quarter of all Chilean cases is reported. Only 10 sporadic cases were found. Segregation analysis of progeny from matings Aa X AY showed p = 0.2206 +/- 0.043. Fertility of 59 obligatory carriers was 3.88 children per mother with a mean age of 49.9 years, a figure higher than the mean of a control population, 3.36. The fertility of hemophiliacs was found to be 2.3 compared with their normal sibs with 3.15 children per couple. Life expectancy at birth in hemophiliacs was 22.4 years, compared with 28.1 for their normal brothers, 34.4 for their sisters and 58.5 and 64.6 for males and females in the general population. Mean relative fitness was calculated as 0.45 and the prevalence of hemophilia A in Chile as 1 case among 13,500 males. A preliminary estimate of the mutation rate was 1.35 X 10-5, within expected ranges. During the last 10 years, family planning and modern treatment with cryoprecipitates have increased the mean age of living hemophiliacs from 12.7 up to 22.7 years, and life expectancy from 15.6 to 22.4 years. Probably relaxation of natural selection will account for a possible increase of new cases of hemophilia A in the near future.