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Haemophilia A and B


Haemophilia A and B


Haemophilia is a hereditary X-linked clotting disorder that can be treated safely and effectively by infusion of clotting factor concentrates


Karin Fijnvandraat MD PhD Amsterdam Hemophilia Treatment Center, Academic Medical Center, Amsterdam, The Netherlands Department of Paediatric Haematology, Emma Children’s hospital, Academic Medical Center, Amsterdam, The Netherlands


Haemophilia is a hereditary clotting disorder that occurs in 1 in 5000 men and is caused by a deficiency of clotting factor VIII (FVIII), resulting in haemophilia A, or a deficiency of clotting factor IX (FIX), resulting in haemophilia B.1,2 Haemophilia is also called the ‘Royal


Disease’ because Queen Victoria was a carrier of haemophilia. Her descendants spread this disease among royal houses throughout Europe. Alexei Nikolaevich, the last Tsar of Russia (1904–1918), was her grandson and suffered from haemophilia. His illness may have influenced history, as his mother hired Rasputin, who treated her beloved son using hypnosis – without effect. This ‘possessed’ monk wielded much influence at the Russian court. The clinical picture of Alexei Nikolaevich is well documented, for instance in the journals of the Tsarina. In 2004, his tomb was found and DNA testing demonstrated that he had suffered from a severe form of haemophilia B.


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Classification of haemophilia When the body is injured, the


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haemostatic process is immediately activated to protect the body’s integrity and to prevent further bleeding. First, platelets are activated at the site of injury. This is followed by sequential activation of clotting factors, eventually resulting in the formation of fibrin. The clotting factors FVIII and FIX are essential for enhancement of the clotting process. FVIII is very susceptible to proteolytic degradation. In plasma, it circulates bound to its carrier protein, von Willebrand factor (VWF).3


The severity of bleeding symptoms in patients with haemophilia depends on the


residual plasma concentration of the deficient coagulation factor. The plasma concentration is expressed in


international units (IU); 1 IU is defined as the concentration of coagulation factor in 1ml of normal plasma. In healthy individuals, the FVIII or FIX plasma concentration varies between 0.50 and 1.50 IU/ml. Alternatively, FVIII or FIX levels are sometimes expressed as percentages of normal (defined as 100%), with corresponding normal levels between 50% and 150%. Patients with haemophilia are classified into three severity groups: severe, moderate and


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