Letters to the Editor

A natural variant with a point mutation resulting in a homozygous Arg to His substitution at position 388 in prothrombin Prothrombin deficiency is probably the rarest inher-ited bleeding disorder with two phenotypes: (i) hypoprothrombinemia, with a concomitant decrease in prothrombin antigen and activity; (ii) dysprothrom-binemia, with a decrease in prothrombin activity but normal or sub-normal antigen levels. Bleeding mani-festations, usually absent in heterozygotes, vary in homozygotes and compound heterozygotes from very mild bleeding to life threatening hemorrhages. In hypoprothrombinemia, the severity of the bleeding manifestations is generally related to the prothrombin level. By contrast, this relationship is much more elu