Abstract
The study of hemophilias A and B performed in the State of Rio Grande do Sul, Brazil, shows that: (a) the frequency of the diseases are the same in Caucasians and Negroids; (b) the ascertained frequency of living cases in the Capital (Pôrto Alegre) is 1:10,000 and in the Interior (23 larger towns) is 1:13,500, the mean age of death being respectively 15 years and 10 years; (c) the relative frequency of hemophilia A[A/(A + B)] is 0.84; (d) the values of p (segregation frequency) and x (frequency of sporadics) are lower than expected, presumably reflecting misclassification of affected as normal by parents and physicians; (e) the prevalence (P) is equal to 177.6 cases, and (f) the total mutation rate in the cities sampled was estimated as being 4.52 × 10–5, which is higher than obtained in other populations. Possibly the population size has been underestimated by inclusion of cases near, but not within, the sampled cities. If the population corresponds to the state of Rio Grande do Sul, the incidence and mutation rate estimates would agree closely with other reports.