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Haemophilia B Brandenberg-type promoter mutation
J A Heit1, R P Ketterling, R E Zapata
1Division of Cardiovascular Diseases, Section of Haematology Research, Department of Medicine, Mayo Clinic and Foundation, Rochester, Minnesota 55905, USA. heitj@rcf.mayo.edu
Summary
This study details the second case of haemophilia B Brandenburg phenotype in a male patient with severe bleeding. A promoter mutation in the factor IX gene was identified, confirming it
Area of Science:
- Hematology
- Genetics
- Molecular Biology
Background:
- Haemophilia B is a genetic bleeding disorder caused by deficiency in coagulation factor IX.
- The Brandenburg phenotype is a rare variant of haemophilia B.
- Understanding factor IX gene mutations is crucial for diagnosing and managing bleeding disorders.
Observation:
- A 17-year-old male presented with severe, persistent bleeding and <1% factor IX activity.
- This is the second confirmed case of the haemophilia B 'Brandenberg' phenotype.
- Genetic analysis revealed a specific G to A transition at nucleotide -26 in the factor IX gene promoter.
Findings:
- The identified mutation (G-->A at bp -26) is located in the factor IX gene promoter region.
- This mutation is associated with the severe Brandenburg phenotype of haemophilia B.
- The patient did not show improvement in factor IX activity post-puberty, contrary to some expectations for promoter mutations.
Implications:
- This case confirms that not all patients with factor IX gene promoter mutations experience clinical improvement after puberty.
- The findings support the hypothesis that the -26 position in the factor IX promoter is a critical binding site.
- This site is important for both constitutive (basal) and androgen-inducible transcription of the factor IX gene.