Transcript Hemophilia
Research Center for Genetic Engineering and Biotechnology “Georgi D. Efremov”, MASA Hemophilia What is: Hemophilia is an X-linked congenital bleeding disorder caused by a deficiency or dysfunctional coagulation factor VIII or factor IX. Hemophilia A is caused by low levels or absence of clotting factor VIII in plasma, affecting 1 in 5,000 males; Hemophilia B is caused by low levels or absence of clotting factor IX in plasma, affecting 1 in 25,000 males Although the two types have very similar signs and symptoms, they are caused by mutations in different genes. A definitive diagnosis depends on factor assay to demonstrate deficiency of FVIII or FIX. Symptoms: The characteristic phenotype in hemophilia is the bleeding tendency. Symptoms in severe hemophilia arose later, when the boy will start walking or running. The severity of bleeding in hemophilia is correlated with the clotting factor level: severely affected individuals have <1 IU/dl (<1% of normal); moderate 1-5 IU/dl (1%-5% of normal); and mild >5 - <40 IU/dl (>5% - <40% of normal) Most bleeding occurs internally into the joints or muscles. Some bleeds can be life-threatening and require immediate treatment Accurate diagnosis of hemophilia is essential to perform appropriate management. Genetics / Inheritance pathways: Hemophilia arises due to mutations in factor VIII (F8) gene – hemophilia A or factor IX gene (F9) – hemophilia B. Both F8 and F9 genes are on X chromosome, thus hemophilia generally affects males. Inheritance is generally trough maternal side. Women have two copies of the X chromosome (XX); They are not affected but they are genetic carriers for hemophilia. Males have only one X chromosome and a Y (XY); those with a faulty clotting factor gene on their X chromosome will have Hemophilia. Analysis performed at RCGEB “Georgi D. Efremov” Intron 1 and intron 22 inversion detection in factor VIII gene Price (МКД) 7.200 Analysis of the coding sequence in the factor VIII gene by DNA sequencing method 50.000 Analysis of the coding sequence in the factor IX gene using DNA sequencing method 15.000 Linkage-analysis for indirect detection of affected X chromosome 10.550 Prenatal diagnosis in a families with high risk of hemophilia 10.550 Carrier detection in a families with known gene defect 10.550 When the mother is a carrier of a hemophilia gene and the father has a normal copy of the gene, in every pregnancy, there is 50% chance that the hemophilia gene would be transmitted to the siblings. (Picture). When the father ihas a hemophilia, all of his daughters would be carriers, while none of his sons would have hemophilia. Genetic testing: The most common gene defect in hemophilia A is intron 22 inversion (45-50%) followed by intron 1 inversion found among 5% of severely affected hemophilia A patients. Moderate and mild phenotypes usually result from missense mutations dispersed through the whole coding region, and are peculiar to individual families. The comprehensive fVIII mutation database (HAMSTeRS) is available at http://hadb.org.uk/. Point mutations, small deletions/insertions dispersed through the whole coding region of the factor IX gene are cause of hemophilia B. Importance of genetic testing: Identifying the disease-causing mutation in males will confirm the diagnosis with certainty Determined molecular defect can predict the severity of disease in newborn child Identifying carrier status among female members of affected families Possibility for prenatal diagnosis in families affected with hemophilia Literature: 1.Online Mendelian Inheritance in Man, http://www.ncbi.nlm.nih.gov/omim; # 306700 (Hemophilia A) # 306900 (Hemophilia B) 2.Castaldo G, et al: Haemophilia A: molecular insights. Clin Chem Lab Med 2007;45(4):450-461 3.Sukarova-Stefanovska E., et al. Molecular characterization of hemophilia A in the Republic of Macedonia. BJMG, 5 (3&4), 27-35, 2002 4.Sukarova Stefanovska E et al., Genetic Inversions among Hemophilia A patients from R. Macedonia and Bulgaria. Acta Haematologica 120:192-194, 2008 RCGEB, 2013