haemophilia(redirected from Haemophiliacs)
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haemophiliaAn X-linked recessive blood clotting disorder causing a life-long tendency to excessive bleeding. It cannot be passed from father to son because the father transmits only the Y chromosome to his sons. All the daughters of a haemophilic man are carriers of the gene but do not suffer the disease. There is a 50% chance that each of their sons will be a haemophiliac. Females can acquire the disease only if both X chromosomes carry the gene. Haemophilia A is due to the absence of Factor VIII, one of the coagulation factors. Haemophilia B (Christmas disease) is due to deficiency of Factor IX. Both feature bleeding, either spontaneous or on minor trauma, most commonly into the joints. This causes severe pain, swelling and muscle spasm. Repeated episodes lead to damage and severe joint disability. Tooth extraction or external injury are followed by prolonged bleeding. Spontaneous bleeding may occur into the bowel. Haemophilia is treated by repeated injections of Factor VIII or IX obtained from donated blood.
haemophiliaa rare human blood disorder in which BLOOD CLOTTING is deficient, resulting often in severe bleeding internally and externally. The condition is due to a lack of fibrin in the blood and is controlled by two closely linked genes on the X-CHROMOSOME that are responsible for the production of different clotting factors. Haemophilia A individuals lack antihaemophilic globulin (AHG) while haemophilia B individuals lack plasma thromboplastin. Males carrying the mutant ALLELE of either locus or (much more rarely) females homozygous for the recessive mutant alleles of either locus will be affected, although heterozygous females have normal blood. Haemophilia A is by far the most common form of the disease (about 80%) and can be treated by transfusions of AHG.
haemophiliainherited coagulation cascade disorder, characterized by lifelong tendency to haemorrhage
haemophilia A; HA deficiency of factor VIII; X-linked recessive condition, expressed almost exclusively in males; characterized by delayed clotting (decreased formation of thromboplastin and reduced conversion of prothrombin)
vascular haemophilia; von Willebrand's disease see disease, von Willebrand's