Webster's New World Medical Dictionary

hemolytic jaundice, congenital
See 
spherocy-
tosis, hereditary.
hemolytic-uremic syndrome
A condition
involving the breakup of red blood cells (hemolysis)
and kidney failure. Abbreviated HUS. HUS is the most
common cause of acute kidney failure in infants and
young children, but the condition can also occur in
adults. The disease results in damage to the lining of
blood vessels in the kidney, leading to destruction of
red blood cells as they pass through damaged ves-
sels. The damaged cells facilitate clot formation in
the blood vessels of the kidneys, which can lead to
kidney failure. Platelet levels are also decreased,
which can cause bleeding problems. HUS most often
occurs after a gastrointestinal (enteric) infection,
caused by a type of 
E. coli
bacteria (
Escherichia coli
O157:H7). HUS may also occur following other types
of gastrointenstinal infections including Shigella and
Salmonella, or it may be related to other conditions
and infections. 
hemophagocytic lymphohistiocytosis
A rare,
cancer-like disorder resulting from an impaired
immune system in which macrophages and lympho-
cytes grow abnormally and accumulate in the body’s
organs, including the liver, spleen, bone marrow,
central nervous system, and skin. Hemophagocytic
lymphohistiocytosis can be an inherited condition,
or it can occur as a result of immunosuppression
(as in organ transplants) or infection. Most patients
are infants or young children. Treatment involves
chemotherapy and in some cases bone-marrow
transplantation. See also 
histiocytosis.
hemophilia
An inherited disorder in which the
ability of blood to clot normally is impaired. There
are two types of hemophilia: hemophilia A and
hemophilia B.
hemophilia A
Classic hemophilia, which is due
to a profound deficiency in the activity of clotting
factor VIII. Affected individuals suffer hemorrhage
into joints and muscles, easy bruising, and pro-
longed bleeding from wounds. The disease is inher-
ited as an X-linked trait, so males are affected and
females carry the gene. Treatment involves adminis-
tration of blood products that introduce clotting fac-
tor VIII and replace lost blood. Use of contaminated
blood products exposed many people with hemo-
philia to HIV infection in the 1980s and 1990s.
Hemophilia A has affected the Russian royal house
and the descendants of Queen Victoria.
hemophilia B
Hemophilia due to deficiency of
coagulation factor IX in the blood, which results in
prolonged oozing after minor and major injuries,
tooth extractions, or surgery. There is renewed
bleeding after the initial bleeding has stopped. The
gene for hemophilia B is on the X chromosome, so
males are affected and females carry the gene.
About 10 percent of carrier females are at risk for
bleeding. Treatment involves administration of
blood products that introduce clotting factor IX and
replace lost blood. Also called Christmas disease
(named for the first patient with the disease to be
studied in detail).
hemoptysis
Spitting up blood or blood-tinged
sputum from the respiratory tract. Hemoptysis
occurs when tiny blood vessels that line the lung air-
ways are broken. Hemoptysis can be harmless such
as from irritated bronchial tubes with bronchitis, or
be serious such as from cancer of the lung.