Experience of a single Italian center in genetic counseling for hemophilia: from linkage analysis to molecular diagnosis

Background and Objectives. We describe our three year experience In genetic counseling at the Castelfranco Veneto Hemophilia Center, Italy. Design and Methods. A total of 258 individuals,were Involved in the study o f 142 females. These formed 40 families with hemophilia A and 6 families,wi th hemophilia B. Following pedigree analysis, the FVIII inversion was first examined in severe hemophilia A patients by polymerase chain reaction (PCR ) analysis. DNA polymorphisms were used to track the affected gene through the remaining families. In uninformative cases, we initiated analysis of th e FVIII or FIX gene coding region by conformation sensitive gel electrophor esis and DNA sequencing to Identify the mutation responsible for the diseas e. Results. The FVIII gene inversion was present in 16 of the 32 patients (50% ) affected by severe hemophilia A and was informative for 44 females. For h emophilia A, 45 cases (55%) were informative by linkage analysis, however 3 7 (45%) were uninformative because of lack of key individuals, homozygosity , or sporadic disease. Information from extragenic linked polymorphisms alo ne was present In 9 cases (6%). For hemophilia B, linkage analysis was info rmative in only 50% of females (8 out of 16). To date, nine mutations have been identified in patients with hemophilia A and three in patients with he mophilia B. six novel missense mutations In hemophilia A are discussed brie fly. interpretation and Conclusions. Using this approach we are now able to offe r accurate genetic analysis to virtually all families with hemophilia. (C) 2000, Ferrata Storti Foundation.