2. Academic Validation
  3. X-linked thrombophilia with a mutant factor IX (factor IX Padua)

X-linked thrombophilia with a mutant factor IX (factor IX Padua)

  • N Engl J Med. 2009 Oct 22;361(17):1671-5. doi: 10.1056/NEJMoa0904377.
Paolo Simioni 1,  Daniela Tormene,  Giulio Tognin,  Sabrina Gavasso,  Cristiana Bulato,  Nicholas P Iacobelli,  Jonathan D Finn,  Luca Spiezia,  Claudia Radu,  Valder R Arruda
Affiliations

Affiliation

  • 1 Department of Cardiologic, Thoracic and Vascular Sciences, University of Padua Medical School, Padua, Italy. paolo.simioni@unipd.it
PMID: 19846852 DOI: 10.1056/NEJMoa0904377
Abstract

We report a case of juvenile thrombophilia associated with a substitution of leucine for arginine at position 338 (R338L) in the factor IX gene (factor IX-R338L). The level of the mutant factor IX protein in plasma was normal, but the clotting activity of factor IX from the proband was approximately eight times the normal level. In vitro, recombinant factor IX-R338L had a specific activity that was 5 to 10 times as high as that in the recombinant wild-type factor IX. The R338 substitution causes a gain-of-function mutation, resulting in factor IX that is hyperfunctional.

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