Sickle Cell (cont.)
What is the outlook (prognosis) for patients with sickle cell
anemia?
The life expectancy
of persons with sickle cell anemia is reduced. Some
patients, however, can remain without symptoms for years, while others
do not survive infancy or early childhood. Nevertheless, with optimal management patients can now
survive beyond the fourth decade.
Most patients suffer intermittent pain crises, fatigue, bacterial
infections, and progressive tissue and organ damage. Impaired growth
and development is the end result of the physical and emotional
trauma that is endured by children with sickle cell anemia.
Causes of death include bacterial infection (the most common cause),
stroke or bleeding into the brain, and kidney, heart, or liver
failure. The risk of bacterial infections does diminish after three
years of age. Nevertheless, bacterial infections are the most common
cause of death at any age. Therefore, any signs of infection in a
person with sickle cell anemia must be reviewed with a doctor to
prevent damage and save lives.
Interestingly, the sickle cell gene somewhat protects against malaria
infection. This makes those with sickle cell trait (gene carriers)
at least partially resistant to malaria. Furthermore, the
geographic distribution of the sickle cell gene is similar to that of
malaria infection. Sickle cell anemia is a lethal condition that
threatens life. But there may be a selective advantage to being a
sickle cell carrier (trait) if the person resides in an area of the
world where malaria is very common. The advantage a person with
sickle cell trait has over a non-carrier of the gene may explain why
sickle cell anemia did not disappear from the world even though it
is lethal.
The sickle cell gene is not a "black gene." It just happens to
disproportionately occur in the black population. When a black
person who carries a sickle cell gene has children with a non-black
person, the children may inherit the sickle cell gene regardless of
their color. There are also non-black persons who carry the sickle
cell gene.
Recent research is examining further ways to promote the development
of the fetal hemoglobin that delays the development of sickle cell in
the newborn. Bone marrow transplantation is being used for patients
with severe sickle cell anemia who have a genetically identical
sibling that can offer the transplant marrow. Future treatments may
involve genetic engineering where cures might be achieved.
Finally, genetic counseling can be helpful for parents and families
to prevent sickle cell anemia. Sickle cell anemia is an inherited
illness. Both parents must be carriers of the sickle cell gene for a
child to be affected with sickle cell anemia. If each parent is a
carrier, any child has a one chance in two (50%) of also being a
carrier and a one in four (25%) chance of inheriting both genes from
the parents and being affected with sickle cell anemia.
- Sickle cell anemia is an inherited disorder of the
hemoglobin in blood.
- Sickle cell anemia requires the inheritance of two sickle cell
genes.
- Sickle cell trait, which is the inheritance of one sickle gene,
almost never causes problems.
- Virtually all of the major symptoms of sickle cell anemia are
the
direct result of the abnormally shaped sickled red blood cells
blocking the flow of blood.
- The current treatment of sickle cell anemia is directed
primarily
toward managing the individual features of the illness as they occur.
Reference:
Bunn, HF. Pathogenesis and treatment of sickle cell disease. N Engl J Med 1997; 337:762.
Harrison's
Principles of Internal Medicine, McGraw-Hill, edited by Eugene Braunwald, et. al., 2001.
Last Editorial Review: 12/4/2006
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