People who have a factor I deficiency have a combined bleeding and clotting disorder, meaning that both platelets and clotting are abnormal. Since its discovery in 1920, there have only been about 200 cases of this disorder. Included under factor I deficiency are several rare coagulation disorders known as congenital fibrinogen defects. The first two are called quantitative abnormalities because they have to do with an absent or low quantity of fibrinogen. The third is called a qualitative abnormality because the fibrinogen does not work well.
Afibrinogenemia is the complete absence of fibrinogen.
Both conditions are inherited in an autosomal fashion and can affect males and females. The severity of the disorder is related to the amount of fibrinogen. Afibrinogenemia is usually discovered in newborns and can cause bleeding from the umbilical cord, genitourinary tract, or central nervous system. People with hypofibrinogenemia may have little, moderate, or severe bleeding. Dysfibrinogenemias are due to variations in the factor I molecule.