DEFICIENCY OF FACTOR X (STUART PROWER FACTOR)

• Biochemical aspects:
  • Factor X is a glycoprotein with a molecular weight of approximately 54,000. It is composed of two polypeptide chains that are linked by one or more disulfide bonds.
  • Factor X is activated by factors IXa and VIII or by factor VII and a tissue factor. In addition, factor X can be activated by trypsin or Russell's viper venom. Protein substrates for factor Xa include prothrombin and factors VII, V, VIII, and IX.
  • A factor X level of 10% to 40% is considered adequate to ensure hemostasis.
• Pathological Basis:
  • Mode of inheritance: autosomal recessive. Approximately 58 cases of hereditary deficiency of factor X have been reported (very rare).
  • A number of acquired states of factor X deficiency have been identified in association with: primary systemic amyloidosis, atypical pneumonia, fungicide exposure.
  • In systemic amyloidosis, the mechanism is apparently the specific adsorption of factor X to amyloid fibrils.
• Treatment:
  • FFP: the usual loading dose is 10 -20 mg of FFP per 10 kg of body weight, followed by 3 -6 mg/kg of body weight every 12 hours.
  • Prothrombin complexe concentrates in life-threatening bleeding and in patients with a severe deficiency of factor X.
  • Avoidance of aspirin-containing compounds.
  • For patients with systemic amyloidosis: splenectomy (these patients will not respond to FFP or prothrombin complex concentrates).