DEFICIENCY OF FACTOR XI (PLASMA THROMBOPLASTIN ANTECEDENT)

• Biochemical aspects:
  • Factor XI is a plasma protein with a molecular weight of approximately 100,000. Native factor XI exists as a dimer of two identical subunits linked by disulfide bonds. It circulates as a proenzyme bound to High-Molecular-Weight- Kininogen (HMWK).
  • Activation of factor XI results from cleavage of each 80,000 dalton subunits by activated factor XIIa . The major physiologic substrate of factor XIa is factor IX.
• Pathological Basis:
  Mode of inheritance: autosomal recessive.
• Treatment:
  • Indication for treatment: preoperative prophylaxis; therepeutically in bleeding patients.
  • Component: FFP, 10-20 ml/kg/day.
  • An activity level of 30% is adaquate for hemostasis.
  • Adjunctive therapy: Amicar (EACA: epsilon-aminocaproic acid) may be used as an adjunct to FFP.