Factor XI and Other Coagulation Factor Deficiencies

I. Review - Factor XI(FXI)

Factor XI is a Vitamin K-dependent serine protease that circulates in the blood in an inactive form.
It is a part of the intrinsic pathway. Once activated to FXIa, it along with FVIII, catalyzes the activation of FIX to FIXa

II. Features of FXI Deficiency

A. Inheritance - autosomal recessive

B. Increased frequency in Ashkenazic Jews (~ 4%)

C. Clinical features

1. Even if severe, the deficiency may be clinically asymptomatic until the patient is challenged by surgical trauma.

2. Bleeding is often induced by surgical trauma in the oropharynx and urinary tract.

3. However, in some instances, bleeding can occur regardless of the severity of the deficiency.

D. Diagnosis - using the specific assay to measure FXI level

E. Treatment

1. Source of FXI for treatment is fresh frozen plasma

2. If patient is having a bleeding episode, keep the FXI level above 30% using FFP infusions.

3. Can also give antifibrinolytic therapy - Aminocaproic acid

4. FXI concentrates - available for compassionate use only in Britain, as of 1995

III. Other Coagulation Protein Deficiencies

A. This includes deficiencies in Factors II, V, VII, X, XIII, and fibrinogen -which are all less common than the hemophilias.

B. Clinical features of these deficiencies include abormal bruising and mucosal hemorrhage.

C. Treatment is with fresh frozen plasma in all of these deficiencies.

D. Cryoprecipitate can also be used for fibrinogen and FXIII deficiencies.