DEFICIENCY OF FACTOR XIII (FIBRIN-STABILIZING FACTOR)

• Biochemical aspects:
  • Factor XIII has two nonidentical-polypeptide subunits, the "a" chain and the "b" chain, that form a tetrameric molecular complex consisting of two a chains and two b chains. The molecular weight of this complex is about 320,000. Once activated by thrombin and calcium, the active cysteine residue on the a chains is exposed and the activated enzyme is formed; followed by dissociation of the b chain dimer from the complex.
  • In its activated form, factor XIII catalyzes the formation of covalent bonds between the gamma chains and alpha chains of fibrin. The consequences of cross-linking are increased mechanical stability of fibrin clots and relative resistance to digestion by plasmin.
• Pathological Basis:
  • Mode of inheritance: autosomal recessive.
  • Deficiency of factor XIII is associated with an increased risk for intracranial hemorrhage.
  • Patients with this disorder lack the a chains and have roughly 50% of the b chain antigenicity normally present in plasma.
• Treatment:
  • Cryoprecipitate or FFP as a prophylactic therapy.
  • Factor XIII concentrates (available in Europe).