Sickle-Cell, Part 1 — Introduction, incidence, and symptoms
What is sickle cell anemia?
Sickle cell anemia, or sickle cell disease, is an inherited disease.
Sickle cell anemia affects the red blood (hemoglobin) cells, which are
normally disc-shaped but are crescent shaped in people with the disease.
As a result of the sickle shape, these blood cells do not function properly
and obstruct small blood vessels, resulting in recurrent painful episodes
called “sickle cell pain crises”.
Sickle cell anemia is caused by an abnormal type of hemoglobin, called
hemoglobin S.
It is an autosomal recessive trait. That means that both parents carried
a recessive gene for hemoglobin S, and that results in the one in four
possibility that a child born to the parents will have sickle cell anemia.
Other conditions include sickle cell – b thalassemia or hemoglobin
SC disease, which occur when hemoglobin S is inherited from one parent
and another type of abnormal hemoglobin is inherited from the other parent.
Someone who inherits hemoglobin S from one parent and normal hemoglobin
A from the other parent will have sickle cell trait. An individual with
sickle cell trait or these other forms of sickle cell disease usually
will have no symptoms. If symptoms are present, they are likely to be
very mild. Occasionally, a person with these conditions will have symptoms
similar to sickle cell anemia.
The course of sickle cell anemia is varied from patient to patient. The
disease becomes life-threatening when damaged red blood cells break down
(called hemolytic crisis), when the spleen enlarges and traps blood cells
(called a splenic sequestration crisis), or when certain infections cause
the bone marrow to stop producing red blood cells (called an aplastic
crisis). Some patients have repeated crises, which can result in damage
to different organs or systems, such as kidneys, lungs, bones, eyes, and
the central nervous system. If a clot occurs in the brain, the person
can suffer a stroke.
Acute painful episodes are referred to as pain crises. These occur when
blood vessels are blocked and/or when organs are damaged by reduced blood
flow. In some patients, these episodes occur only once every few years;
in others, pain crises may occur several times a year. The duration of
these crises may be hours to days, and may require hospitalization for
pain control and/or intravenous fluids. The bones of the back, the long
bones of legs and arms, and the chest are areas most often affected by
a pain crisis.
The sickled red blood cells are very fragile and inflexible and many of
the disease manifestations are a result of the fragility and inflexibility
of the crescent shaped cells. Dehydration, infection and low oxygen supply
result in sickling of red blood cells and, subsequently, destruction and
poor flow of these cells through the blood vessels. Thus, oxygen is not
supplied to the body’s tissues as needed.
Sickle cell anemia is usually diagnosed at birth by a test that is required
by law and routinely performed in all states. The disease can now be diagnosed
before birth, as early as the first trimester, by chronic villus sampling.
Incidence and Prevalence
Sickle cell disease is much more common in certain ethnic groups. It
is believed that this genetically different hemoglobin evolved as a protection
against malaria, because people with sickle trait were more likely to
survive malaria outbreaks in Africa than those individuals with normal
hemoglobin. Thus, many survivors in geographic areas where malaria was
a problem survived to pass sickle cell disease and sickle cell trait on
to their offspring. In addition to persons from Africa, sickle cell is
found in individuals from Mediterranean descent and in Native Americans.
Approximately one out of every 500 African Americans are effected by sickle
cell disease. Approximately 8%, or one in 12, African Americans have sickle
cell trait.
Symptoms
Symptoms vary greatly from person to person, but there are symptoms that
are typical in sickle cell anemia. Those symptoms may include:
- Hand and foot pain
- Fatigue
- Joint and bone pain
- Frequent infections
- Jaundice
- Abdominal pain
- Chest pain
- Shortness of breath
- Rapid heart rate
- Fever
- Ulcers on lower legs
- Delayed growth
- Delayed puberty
- Excessive thirst
- Excessive urination
- Bloody urine
- Poor eyesight
- Priapism (unwanted, painful erection)
Patients with sickle cell anemia may appear pale and there may be a noticeable
yellowness in the eyes and/or skin. Crises may be induced by infection,
exposure to extreme temperatures of hot or cold, a blow to the body, lack
of adequate fluid intake or excessive physical exertion.
Sickle-Cell, Part 1 — Introduction, incidence, and symptoms
For more information, please contact:
Kathy Davis, MSEd, PhD
kdavis2@kumc.edu
(913) 588-6305