Hemophilia refers to a group of bleeding disorders in which there is a deficiency of one of the factors necessary for coagulation of the blood. Although the symptomatology is similar despite the missing factor, the identification of specific factor deficiencies has allowed definitive treatment with replacement agents. The two most common forms of the disorder are classic hemophilia (hemophilia A or factor IX deficiency). The following discussion is primarily concerned with the classic form, which accounts for about 75% of all cases.
A major feature of hemophilia is that its expression varies markedly in the degrees of bleeding severity. Hemophilia is generally classified into three groups according to the severity of factor deficiency.
1. Severe defects with less than 1% of the normal amount of factor; affected individuals bleed spontaneously or from minor trauma and literally may die from exsanguinations
2. Moderate defects with levels of 1% to 5% affected individuals usually bleed after some type of trauma but do not bleed spontaneously
3. Mild defects with levels ranging between 5% and 25% affected individuals manifest bleeding tendencies after they sustain a serious injury or undergo surgery, such as dental extraction or tonsillectomy.
In about 80% of cases of hemophilia, the inheritance is demonstrated as an X-linked recessive disorder. The most frequent pattern of transmission is between an unaffected male and a trait-carrier female with improved treatment for persons with hemophilia, it is important to consider the results of mating between an affected male and normal female or a carrier female. For example, the mating of an affected male with a carrier female results in a 1:4 chance of producing either an affected son or daughter, a carrier daughter, or a normal son. This is one of the few ways in which a female can become a hemophiliac.
Other reasons for female expression of the disease include
1. A "symptomatic" earner of classic hemophilia with a moderate defect of factor VIII
2. a phenotypic female who has inherited the recessive gene for hemophilia but lacks the second X chromosome, as in Turner's syndrome
3. A female with an autosomal dominant transmitted form of factor VIII deficiency, such as von willebrands's disease
4. A female with severe factor deficiency whose parents are normal or chromosomal aberration.
Pathophysiology
In hemophilia A the factor VIII molecule is present but is defective in its clotting function. Factor VIII-related antigen (FVIIIR:Ag) is normal. In hemophilia B there may be a defect or a deficiency of factor IX.
Clinical manifestations
The effect of hemophilia is prolonged bleeding anywhere from or in the body. With severe factor deficiencies hemorrhage can occur as a result of minor trauma, such as after circumcision, during loss of deciduous teeth, or as a result of a slight fall or bruise.
Subcutaneous and intramuscular hemorrhages are common, Hemarthrosis, bleeding into the joint cavities, especially the knees, ankles, and elbows, is the most frequent site of internal bleeding and often results in bone changes and consequently crippling, disabling deformities, spontaneous hematuria is not uncommon, Epistaxis mau occur but is not as frequent as other kinds of hemorrhage.
Bleeding into the tissue can occur anywhere but is serious if it occurs in the neck, mouth, or thorax, since the airway can become obstructed, Intracranial hemorrhage can result in fatal consequences, although this occurs less frequently than expected because the brain tissue has a high concentration of thromboplastin. Hemprrhage anywhere along the gastrointestinal tract can lead to obstruction, melena and vomiting with blood. Hematomas in the spinal cord can cause paralysis.
Petechiae are uncommon in persons with hemophilia because repair of small hemorrhages is dependent on platelet function, not on blood-clotting mechanisms
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