Combined Deficiency of Factor V and Factor VIII: Report of a Family and Genetic Analysis

S ummary . A family, in which the combined deficiency of factor V and factor VIII is segregating, is described. It is the first family reported which was detected through routine coagulation studies and the first one in which paternal relatives are found to be affected as well as maternal relatives. Over 40 family members have been studied. A review of the genetic hypotheses in the literature is presented. The data from this family and from the previously reported ones are analysed as to the mode of inheritance. An autosomal recessive mode of inheritance with a marked degree of penetrance (27.2–72.8%) and varying expressivity in heterozygotes seems to be the most likely explanation. The aims for further studies are outlined.