About Haemophilia In Germany approximately 9,000 patients suffer from haemophilia A or B with different intensity. Haemophilia, also known as a bleeding disorder, is a genetic blood clotting disorder with X-chromosomal recessive heredity. The genetic mutation leads to a deficiency of the blood clotting factors VIII (haemophilia A) or IX (haemophilia B), which causes extended partial thromboplastin time and thus bleeding for longer periods of time. As a result of this, frequent spontaneous muscle and joint bleeds occur, which in turn may lead to morphologic and neuromuscular changes in the joints. One of the most frequent joint diseases amongst haemophilic patients is the haemophilic arthropathy. This secondary, inflammatory form of arthrosis is the consequence of recurrent bleedings in the joint. The haemophilic joint and arthropathy are the main issue during the course of severe haemophilia A and B. For patients this means distinct consequences on everyday life and quality of life. Due to the X-chromosomal heredity haemophilia primarily affects males. Female carriers frequently show a reduced factor VIII or IX activity but because of the second, healthy X-chromosome they only have symptoms of mild haemophilia. In most cases this blood clotting disorder is inherited. However, in as many as 30% to 40% of cases, there is no positive family history of haemophilia, which confirms the assumption of a high rate of spontaneous mutation. There is a distinction between haemophilia A and haemophilia B. The incidence of haemophilia A, also called classical haemophilia, is one in 5,000 - 10,000. Haemophilia B (synonym: Christmas disease) with an incidence of one in 25,000 – 50,000 live male births is five times less common than haemophilia A. The clinical degree of severity is defined by the activity of factor VIII or IX. The reduced activity is referred to as rest activity and stated in percent of the norm (F VIII: 60 – 150%, F IX: 70 – 130%). Table 1 shows the classification of the various haemophilia courses due to the residual activity of the respective clotting factor: Degrees of severity Residual factor activity in % Bleeding incidences Severe haemophilia (Haemophilia gravis) <1 Spontaneous bleeding in joint and muscles Moderate haemophilia (Haemophilia intermedia) 1 - < 5 Moderate frequent spontaneous bleeds; severe bleeds after minor surgical operations Mild haemophilia (Haemophilia mitis) 5 - < 40 Rare spontaneous bleeds; bleeds after minor surgical operations. Bleeding tendency after major operations and severe traumas Based on the clinical picture of spontaneous bleedings with a residual factor activity of 3% a further distinction is possible. Patients with F VIII or F IX - activity less than 3% tend to experience spontaneous bleedings without any traumatic impact.