title: Congenital factor XI and factor VII deficiencies assure an apparent opposite protection against arterial or venous thrombosis: An intriguing observation.
abstract: OBJECTIVE
  To investigate the prevalence and type of thrombotic events reported in patients with congenital factor XI (FXI) or factor VII (FVII) deficiency.
  
  
  METHODS
  Data on all patients with congenital FXI or FVII deficiency and a thrombotic event were gathered by means of a time unlimited PubMed search carried out in June 2014 and in February 2015. Appropriate keywords including the medical subject headings were used in both instances. Side tables were also consulted and cross-checking of the references was carried out to avoid omissions. The thrombosis event had to be proven by objective methods.
  
  
  RESULTS
  Forty-three patients with FXI deficiency had arterial thrombosis and only eight had venous thrombosis. On the contrary, only five patients with FVII deficiency had arterial thrombosis whereas 31 patients had venous thrombosis. The arterial/venous ratios were 5.37 and 0.17 for FXI or FVII, respectively.
  
  
  CONCLUSIONS
  Arterial thrombosis is frequent in FXI deficiency whereas venous thrombosis is rare. The reverse is true for FVII deficiency. The significance of these findings is discussed especially in view of the recent use of synthetic anti-FXI compounds in the prophylaxis of post-orthopedic surgery of venous thrombosis complications.
authors.affiliation: a Department of Medicine , University of Padua Medical School , Italy.
authors.forename: A
authors.initials: A
authors.lastname: Girolami
authors.affiliation: a Department of Medicine , University of Padua Medical School , Italy.
authors.forename: E
authors.initials: E
authors.lastname: Peroni
authors.affiliation: b Division of Medicine , Padua City Hospital , Italy.
authors.forename: B
authors.initials: B
authors.lastname: Girolami
authors.affiliation: a Department of Medicine , University of Padua Medical School , Italy.
authors.forename: S
authors.initials: S
authors.lastname: Ferrari
authors.affiliation: a Department of Medicine , University of Padua Medical School , Italy.
authors.forename: A M
authors.initials: AM
authors.lastname: Lombardi
mesh_terms: D005168:Factor VII Deficiency / Q000235:genetics*; D005172:Factor XI / Q000235:genetics*; D006801:Humans; D020246:Venous Thrombosis / Q000235:genetics*
chemical_list: D005172:Factor XI
keywords: Arterial thrombosis; FXI; Factor VII; Venous thrombosis