Hemophilia A is a disease of the blood
Pathophysiology
congenital coagulation disorder due to a defect in factor 8 (synthesized in liver), which is complexed to von Willebrand factor (vWF)
Signs and Symptoms
1) bleeding into soft tissues, muscles, joints, typically hours to days after trauma 2) mass effect of accumulated blood can cause compartment syndrome 3) most serious areas of bleeding are into oropharynx and CNS 4) often presents with diffuse bleeding at circumcision
Characteristic Test Findings
Laboratory – 1) factor 8 < 5% of normal 2) prolonged PTT (other bleeding tests are usually normal) 3) increased AST and ALT
Histology/Gross Pathology
1) hemarthrosis 2) synovial inflammation 3) erosion of articular cartilage 4) osteoarthritis 5) articular fibrosis 6) pseudophlebitis from venous congestion 7) ischemic damage to nerves
Inheritance/Epidemiology
1) affects 1/10,000 males 2) transmitted in X-linked mode 3) female carriers occasionally have inactivation of normal X gene with major bleeding
Treatment
1) concentrated factor 8 or cryoprecipitate (contains factor 8) 2) in mild cases can use DDAVP 3) aim is to get factor 8 levels to 25% to stop active bleeding or to 50% as prophylaxis for major surgery (often requires 2-3 weeks of therapy) 4) the presence of inhibitors to factor 8 should be checked before treatment
Tips for USMLE
1) look for a patient who has an increased PTT and a normal PT, bleeding time, and platelet count 2) never use aspirin products in hemophilia A patients
Leave a Reply