title: Congenital hypersensitivity to vitamin K antagonists due to FIX propeptide mutation at locus -10: a (not so) rare cause of bleeding under oral anticoagulant therapy in Switzerland.
abstract: OBJECTIVE
  In most countries hypersensitivity to vitamin K antagonists (VKA) is considered to be a rare congenital bleeding diathesis. It occurs in patients with FIX propeptide mutations at locus -10. We present a Swiss family with two patients who suffered major bleedings under oral anticoagulant treatment in the presence of therapeutic or subtherapeutic INR levels and abnormally prolonged aPTT. In both patients a mutation in the propeptide of FIX at locus -10 with substitution of alanine by threonine (Ala-10Thr) was found. In one patient FIX clotting activity was found to be severely reduced (2%). The observed bleeding tendency is related to this--compared to the other vitamin K dependent factors (FII, FVII, FX)--excessively and disproportionately low level of FIX. Three generations of this family were tested for propeptide mutations, which are transmitted in an X-chromosomal recessive mode of inheritance. Apart from the two symptomatic male patients we found another male with the mutation who has not been exposed to VKA, six female carriers and four potential male carriers in the fourth generation who have not been tested. A founder effect for this mutation has been previously described for cases in Switzerland and Germany.
  
  
  CONCLUSIONS
  FIX propeptide mutation-associated hypersensitivity to VKA is a rare occurrence in Switzerland. The severity of associated bleeding complications and the reversible nature of the bleeding diathesis may nonetheless warrant increased awareness on the part of primary care physicians in Switzerland.
authors.affiliation: Department of Internal Medicine, University Hospital, Ramistrasse 100, Zurich, Switzerland. silvia.ulrich@usz.ch
authors.forename: Silvia
authors.initials: S
authors.lastname: Ulrich
authors.forename: Brigitte
authors.initials: B
authors.lastname: Brand
authors.forename: Rudolf
authors.initials: R
authors.lastname: Speich
authors.forename: Johannes
authors.initials: J
authors.lastname: Oldenburg
authors.forename: Lars
authors.initials: L
authors.lastname: Asmis
mesh_terms: D000368:Aged; D000409:Alanine / Q000235:genetics; D019943:Amino Acid Substitution; D000925:Anticoagulants / Q000009:adverse effects*; D003374:Coumarins / Q000009:adverse effects*; D004342:Drug Hypersensitivity / Q000235:genetics*; D005164:Factor IX / Q000235:genetics*; D019918:Heart Valve Prosthesis Implantation; D006470:Hemorrhage / Q000139:chemically induced*; D006579:Heterozygote; D006801:Humans; D019934:International Normalized Ratio; D008297:Male; D009154:Mutation; D010314:Partial Thromboplastin Time; D010375:Pedigree; D011498:Protein Precursors / Q000235:genetics; D013557:Switzerland; D013912:Threonine / Q000235:genetics; D014812:Vitamin K / Q000037:antagonists & inhibitors
chemical_list: D000925:Anticoagulants; D003374:Coumarins; D011498:Protein Precursors; D014812:Vitamin K; D013912:Threonine; D005164:Factor IX; C030123:coumarin; D000409:Alanine