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Gene deletions in patients with haemophilia B and anti-factor IX antibodies
Insights
Christmas disease (haemophilia B) is an X-linked disorder where patients lack clotting factor IX. Researchers investigated gene defects, finding four patients with gross factor IX gene abnormalities, potentially explaining antibody development during treatment.
Area of Science:
- Genetics
- Hematology
- Immunology
Background:
- Christmas disease (hemophilia B) is an inherited X-linked bleeding disorder.
- Patients have a deficiency in clotting factor IX.
- Treatment involves factor IX replacement, but anti-factor IX antibodies can complicate therapy.
Purpose of the Study:
- To investigate the genetic basis of factor IX deficiency in patients with Christmas disease.
- To determine if gross defects in the factor IX gene could explain the development of anti-factor IX antibodies.
Main Methods:
- Utilized a previously isolated gene probe to test for factor IX gene defects.
- Analyzed DNA from patients with Christmas disease.
Main Results:
- Identified four patients with gross defects in the factor IX gene.
- These genetic abnormalities may lead the immune system to recognize infused factor IX as foreign.
Conclusions:
- Gross factor IX gene defects are present in some patients with Christmas disease.
- This genetic absence may underlie the immune response observed during factor IX replacement therapy.
Abstract:
Christmas disease, or haemophilia B, is an inherited X-linked haemorrhagic disease which at present occurs in 798 known cases in the United Kingdom, corresponding to a frequency of about 1 in 30,000 males. Patients are deficient in the intrinsic clotting factor IX and are treated by replacement of this protein prepared from pooled plasma obtained from normal individuals. Occasionally treatment is complicated by the appearance of specific anti-factor IX antibodies. It seemed to us that this might be due to the absence of 'self' factor IX causing the immune system to regard the infused normal factor IX as foreign. The absence of all or part of the factor IX gene was an obvious possible reason for this, which we have now tested using our previously isolated gene probe. We have found four patients with gross gene defects.