Hemophilia A is an X-linked, recessive disorder caused by deficiency of functional plasma clotting factor VIII, which may be inherited or arise from spontaneous mutation. Factor VIII deficiency, dysfunctional factor VIII, or factor VIII inhibitors disrupt the normal intrinsic coagulation cascade. Trauma to any part of the body can cause deep bleeding and result in significant hemorrhage. Hemorrhage sites include joints (eg, knee, elbow); muscles; the central nervous system ; and the gastrointestinal, genitourinary, pulmonary, and cardiovascular systems. Spontaneous hemorrhage has also been reported. Intracranial hemorrhage occurs most often in patients younger than 18 years due to inherent risk for direct head trauma from a greater amount of physical activity. With an estimated mortality rate of 20%, intracranial hemorrhage accounts for the highest number of deaths in patients with hemophilia and is a common cause of long-term disability for survivors.
Petechiae usually do not occur in patients with hemophilia A. Petechiae do not represent deep bleeds and are clinical indicators of capillary blood leakage, which is typically the result of vasculitis or abnormalities in the number or function of platelets.
Patients considered to have the mild form of hemophilia A may not be diagnosed for years and may have bleeding episodes after surgery or major trauma. In the moderate form, affected patients usually experience bleeding following mild-to-moderate injuries. In the severe form, patients experience spontaneous bleeding and hemorrhage after minor trauma up to about 6 times a month, including hemarthrosis and intramuscular hemorrhage.
The aPTT assay is a screening test used to evaluate the overall integrity of the intrinsic/common coagulation pathway. Usually, the aPTT is prolonged in patients with hemophilia A or B; however, a normal aPTT (reference range, 30-40 seconds) does not exclude the mild or moderate forms of hemophilia because of the relative insensitivity of the test. The aPTT is significantly prolonged in severe hemophilia (> 70 seconds).
Desmopressin vasopressin analog, or 1-deamino-8-D-arginine vasopressin (DDAVP), can be used to treat minor bleeding episodes or used for prophylaxis of minor surgical/invasive procedures in patients with hemophilia A who have a low inhibitor titer and measurable baseline levels of circulating Factor VIII; hence, it can help patients with mild and moderate hemophilia A. Unfortunately, DDAVP is not effective in treatment of patients with severe hemophilia.
For more information on hemophilia A, read here.
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Cite this: Germaine L. Defendi. Fast Five Quiz: Inherited Conditions - Medscape - Oct 29, 2018.