However, there was a discrepancy between the factor IX antigen determined by the neutralization test and the factor IX procoagulant activity in the patients of both hemophilia BM and hemophilia B+.
52 kindreds, referred to as haemophilia B-, were characterized by severe deficiency of factor IX coagulant activity (less than 0.01--0.03 u/ml) and unmeasurable IX:Ag (less than 0.12 u/ml): this genetic variant of the disease appears to be related to a complete or marked suppression of factor IX synthesis.
The authors studied the effect of averaging replicated assays of Factor IX coagulation activity and Factor IX antigen on each plasma specimen in improving the ability to detect carriers of hemophilia B.
This variant of factor IX has been demonstrated in the plasma of a patient with severe haemophilia B and in the plasmas of a number of possible carriers from the probands' pedigree.
It is concluded that the quantitative determination of factor IX antigen may be of value in the detection of carriers of both haemophilia B+ and haemophilia B-.
With this assay, 11 of 12 patients with severe hemophilia B had factor IX antigen levels below 1 U/dl and 6 patients with mild hemophilia B had various levels.
Hemophilia B Chapel Hill is a mild hereditary hemorrhagic disorder in which the factor IX antigen is present in normal amounts but factor IX biological activity is markedly reduced.
DNA from a patient with severe factor IX deficiency (haemophilia B) in whom an inhibitor to factor IX had developed was studied with four genomic gene probes specific for the factor IX gene.
This genetic marker was used, in parallel with coagulation and immunological assays, to follow the segregation of an abnormal FIX gene in a large Hemophilia B family.
Haemophilia B (Christmas disease) is an inherited, recessive, sex-linked, haemorrhagic condition caused by a defect in the intrinsic clotting factor IX.
Characterization of three abnormal factor IX variants (Bm Lake Elsinore, Long Beach, and Los Angeles) of hemophilia-B. Evidence for defects affecting the latent catalytic site.
A functional deficiency of factor IX underlies haemophilia B, a chromosome X-linked recessive disease for which the major therapeutic approach is replacement treatment using factor IX concentrates.
The disease is characterized by a normal ox-brain prothrombin time, normal levels of the vitamin-K dependent clotting factors VII and X and a proportional reduction of factor IX activity and antigen levels all of which is consistent with the cross-reacting material negative form of haemophilia B.
We show that a point mutation causing hemophilia B changes the amino acid at position -4 in the propeptide region of factor IX from an arginine to a glutamine, which results in the expression of a stable longer protein with 18 additional amino acids of the N-terminal propeptide region still attached.