Uses for Recombinant Protein Drugs - Biotechnology and Your Health: Pharmaceutical Applications - page 66

been recognized from ancient times as an inherited tendency
(mainly in males) to bleed excessively even after a minor wound.
This life-threatening condition affected the last Russian royal
family (the Romanovs, who died in 1918) and many of their rel-
atives among other European royalty. There are about 20,000
people, mostly men, living with hemophilia in the United States.
Worldwide, the prevalence of the disease varies from country to
country, but there are probably 200,000 to 400,000 people around
the world with hemophilia.
Many proteins and cells are involved in the complicated process
that causes blood to change from a liquid to a solid, which is what
happens in blood clotting . Errors in the genes that code for any of
these proteins may put a person at risk of severe bleeding—even
bleeding to death—from a minor cut. Hemophilia A and B, the
most common forms, result from errors in two different clotting
protein genes carried on the X chromosome. Because the genes are
on the X chromosome, males (who have an XY chromosome
arrangement) only have to receive one defective gene to suffer from
bleeding problems. Carrier females (women have two X chromo-
somes) with one normal and one defective copy of the gene
generally do not experience bleeding problems, but their sons have
a 50% chance of inheriting the defective gene and suffering from the
disease. Women can have hemophilia, but because they must have
inherited a copy of the defective gene from both parents, it is very
rare. Hemophilia A and B are the result of inherited defects in two
different proteins, called factors, both part of the cascade of steps
that allows blood to clot. Males with hemophilia A have inherited a
defective version of the gene for the Clotting Factor 8; those with a
defective copy of the gene for Clotting Factor 9 have hemophilia B.
Hemophiliacs are treated with clotting factors when they have
severe bleeding episodes, and are also treated to prevent bleeding if
surgery or any other activity that might lead to bleeding is planned.
Before recombinant technology, the fluid part of normal human