title: Coexistence of hereditary homocystinuria and factor V Leiden--effect on thrombosis.
abstract: BACKGROUND
  Venous and arterial thromboembolism occurs in only about one third of patients homozygous for homocystinuria, which suggests that other, contributory factors are necessary for the development of thrombosis in these patients. Factor V Leiden, an R506Q mutation in the gene coding for factor V, is the most common cause of familial thrombosis and could be a potentiating factor.
  
  
  METHODS
  We determined activated partial-thromboplastin times in the presence and absence of activated protein C and tested for the factor V Leiden mutation in 45 members of seven unrelated consanguineous kindreds in which at least 1 member was homozygous for homocystinuria.
  
  
  RESULTS
  Thrombosis (venous, arterial, or both) occurred in 6 of 11 patients with homocystinuria (age, 0.2 to 8 years). All six also had the factor V Leiden mutation. One patient with prenatally diagnosed homocystinuria who was also heterozygous for factor V Leiden has received warfarin therapy since birth and has not had thrombosis (age, 18 months). Of four patients with homocystinuria who did not have factor V Leiden, none had thrombosis (ages at this writing, 1 to 17 years). Three women who were heterozygous for both homocystinuria and factor V Leiden had recurrent fetal loss and placental infarctions.
  
  
  CONCLUSIONS
  Patients with concurrent homocystinuria and factor V Leiden can have an increased risk of thrombosis. Screening for factor V Leiden may be indicated in patient with homocystinuria and their family members.
authors.affiliation: Department of Pediatrics, Rambam Medical Center, Haifa, Israel.
authors.forename: H
authors.initials: H
authors.lastname: Mandel
authors.forename: B
authors.initials: B
authors.lastname: Brenner
authors.forename: M
authors.initials: M
authors.lastname: Berant
authors.forename: N
authors.initials: N
authors.lastname: Rosenberg
authors.forename: N
authors.initials: N
authors.lastname: Lanir
authors.forename: C
authors.initials: C
authors.lastname: Jakobs
authors.forename: B
authors.initials: B
authors.lastname: Fowler
authors.forename: U
authors.initials: U
authors.lastname: Seligsohn
mesh_terms: D000293:Adolescent; D001483:Base Sequence; D001778:Blood Coagulation Disorders / Q000150:complications / Q000235:genetics; D002648:Child; D002675:Child, Preschool; D005165:Factor V / Q000235:genetics*; D005260:Female; D006712:Homocystinuria / Q000150:complications* / Q000235:genetics; D006801:Humans; D007223:Infant; D008297:Male; D008969:Molecular Sequence Data; D010375:Pedigree; D017354:Point Mutation; D011486:Protein C / Q000235:genetics / Q000378:metabolism; D012307:Risk Factors; D013927:Thrombosis / Q000209:etiology / Q000235:genetics*
chemical_list: D011486:Protein C; D005165:Factor V