© 2014 Direct One Communications, Inc. All rights reserved. 1 Genetics of Hemophilia: The Role of Genetic Testing and the Use of Genetics to Guide Treatment Anna Chalmers, MD Rush University Medical Center, Chicago, Illinois A REPORT FROM THE 65 TH ANNUAL MEETING OF THE NATIONAL HEMOPHILIA FOUNDATION (NHF 2013) AND THE 55 TH ANNUAL MEETING OF THE AMERICAN SOCIETY OF HEMATOLOGY (ASH 2013)

© 2014 Direct One Communications, Inc. All rights reserved. 2 The Genetic Basis of Hemophilia Hemophilia is a hereditary disease caused by deficiencies in coagulation factors VIII (hemophilia A) and IX (hemophilia B) due to mutations of the F8 and F9 genes on the X chromosome. Deletion and insertion mutations and mutations that cause premature termination of synthesis usually cause severe disease. Certain missense mutations also can lead to severe hemophilia. More commonly, missense mutations cause mild or moderate disease; in fact, 90% of patients who have mild-to-moderate hemophilia A have missense mutations. The majority of patients with hemophilia B also have missense mutations.

© 2014 Direct One Communications, Inc. All rights reserved. 3 Who Should Have Genetic Testing The Medical and Scientific Advisory Committee for the National Hemophilia Foundation recommends that all hemophilia patients have genotype testing; an initiative is underway to create a comprehensive de-identified database of these mutations. Appropriate family members can also undergo genetic testing to determine carrier status. In pretesting counseling, only about 30% of cases of hemophilia are sporadic; despite this finding, most carriers are unaware of their status and will require supportive counseling. National Hemophilia Foundation Web site. MASAC recommendations on the NHF Genotyping Project for persons with hemophilia. November 1, 2009; Pruthi RK. Mayo Clin Proc. 2005;80:1485

© 2014 Direct One Communications, Inc. All rights reserved. 4 Who Should Have Genetic Testing In testing possible carriers, it is best to target a known mutation. If the mutation is unknown, then the approach is similar to testing patients with hemophilia: first screen for an intron 22 inversion mutation, as it is the most common overall cause of unspecified hemophilia. If this test is negative, then screen the whole gene. Pruthi RK. Mayo Clin Proc. 2005;80:1485

© 2014 Direct One Communications, Inc. All rights reserved. 5 Who Should Have Genetic Testing Carrier status affects preconception counseling. It is important to discuss family planning options, including preimplantation genetic testing, with carriers. Patients who are carriers and are pregnant with male fetuses need to be followed by a multidisciplinary team of specialists throughout the pregnancy to address any possible perinatal testing and ensure a safe delivery. National Hemophilia Foundation Web site. MASAC recommendations on the NHF Genotyping Project for persons with hemophilia; November 1, 2009

© 2014 Direct One Communications, Inc. All rights reserved. 6 Using Genetics to Guide Treatment A small percentage of hemophilia patients with severe disease, as defined by coagulation factor level, have a milder-than-expected clinical presentation; this observation has generated interest is using genetic information to help guide management decisions. Carcao and coworkers examined 621 previously untreated patients and classified them according to whether they carried null or non-null mutations. Patients with null mutations experienced their first hemarthrosis at a younger age, but the difference was only 2 months. Santagostino E et al. J Thromb Haemost. 2010;8:737; Carcao MD et al. Blood. 2013;121:3946

© 2014 Direct One Communications, Inc. All rights reserved. 7 Using Genetics to Guide Treatment Most patients with an inhibitor phenotype have large alterations, such as large deletions, nonsense mutations, or frameshift mutations, in F8 or F9. A small percentage of patients with this phenotype can develop anaphylaxis to replacement factor, a life- threatening, difficult-to-manage clinical situation. » Eight patients with hemophilia B who had experienced anaphylaxis to FIX were genotyped and compared to patients with severe disease; those who had complete gene deletions were at the highest risk of developing anaphylaxis. » Patients with major gene mutations who are at high risk of anaphylaxis may need to be infused in the supervised clinic setting instead of receiving treatment at home. Thorland EC et al. Haemophilia. 1999;5:101