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Keywords:

  • combined FV + FVIII deficiency;
  • F5F8D;
  • LMAN1;
  • MCFD2

Summary.  Inherited deficiencies of plasma proteins involved in blood coagulation generally lead to lifelong bleeding disorders. The severity of these disorders is generally inversely proportional to the degree of factor deficiency. Among all the autosomal recessive rare bleeding disorders, which include afibrinogenaemia, factor (F) II, FV, FV + VIII, FVII, FX, FXI, FXIII, the combined deficiency of coagulation FV and FVIII (F5F8D or FV + FVIII) is exceptional because it is due to mutations in genes encoding proteins involved in the FV and FVIII intracellular transport (LMAN1 and MCFD2) rather than DNA defects in the genes that encode the corresponding coagulation factors. F5F8D is estimated to be extremely rare (1:1.000.000) in the general population, but an increased frequency is observed in regions where consanguineous marriages is practiced. F5F8D is characterized by concomitantly low levels (usually between 5% and 20%) of both FV and FVIII, and is associated with a mild to moderate bleeding tendency. Treatment of bleeding episodes requires a source of both FV and FVIII; replacement of FV is achieved through the use of fresh frozen plasma, and that of FVIII by desmopressin or specific FVIII concentrates, plasma-derived or recombinant FVIII products. We focus here on the clinical, molecular, treatment-related and diagnostic features of F5F8D.