State of the art of genetic studies in hemophilia carriers.

The new molecular tools and, remarkably the next-generation sequencing (NGS), have driven not only rapid and confident genetic counseling and prenatal diagnosis in hemophilia but also advanced reproductive alternatives, such as preimplantation and noninvasive prenatal diagnoses. Moreover, such tools also allow the research and provide solutions to other problems associated with women carriers of hemophilia. For example, the study of unbalanced inactivation of the X chromosomes as etiology of hemorrhagic symptoms in women. Also allow to perform genetic studies in sporadic hemophilia (i.e., families without a previous disease history). Determining the origin of the mutation in such families is crucial since has important consequences for genetic counseling and prenatal diagnosis. With the new technological alternatives, it is possible to detect mosaicisms, improving the prediction of the likelihood of hemophilia transmission. However, the most revolutionary in carrier genetics will probably arrive in the coming years with the global application of NGS to studies that will allow, for example, to identify the presence of fetal mutations in the mother's plasma sample or the establishment of the complete genome sequencing as a routine widespread practice in newborns.