Sickle cell anemia
Alternative names:
anemia - sickle cell; Hemoglobin SS disease (Hb SS); Sickle
cell disease.
Definition:
An inherited, chronic
blood disease in which the red blood cells become crescent
shaped and function abnormally. As a result, they function
abnormally and break down, causing recurrent painful episodes.
Causes, incidence, and risk factors:
Sickle cell anemia, which is caused by an abnormal type
of hemoglobin (oxygen
carrying pigment) called hemoglobin S It is inherited as an
autosomal recessive trait. It occurs in people who have inherited
hemoglobin S from both parents. If hemoglobin S is inherited
from one parent, the offspring will have sickle
cell trait.Someone who inherits hemoglobin S from one
parent and another type of abnormal hemoglobin from the other
parent will have another form of sickle cell disease such
as sickle cell-b0 thalassemia, hemoglobin SC disease, or sickle
cell-b+ thalassemia. Someone with sickle cell trait or these
forms of sickle cell disease will usually have no symptoms
or only mild ones. However, some of these conditions can cause
symptoms similar to sickle cell anemia.
The disease occurs primarily in people of African Heritage,
with 1 out of 400 African-Americans affected. The disease
produces a chronic anemia
which may become life-threatening when hemolytic crises (the
breakdown of red blood cells) or aplastic
crises (bone marrow fails to produce blood cells) occur. Repeated
crises can lead to damage of the kidneys, lungs, bone, liver,
and central nervous system.
Acute painful episodes
caused by blocked blood vessels and damaged organs may occur
and last hours to days affecting the bones of the back, the
long bones, and the chest.
Sickle cell anemia may become life threatening when damaged
red blood cell break down (hemolytic crisis) or bone marrow
fails to produce blood cells (aplastic crises). Repeated crises
can cause damage to the kidneys, lungs, bone, liver (incidence
less than two percent), and central nervous system. Blocked
blood vessels and damaged organs can cause acute painful episodes.
These painful crises, which occur in 70% of patients, can
last hours to days, affecting the bones of the back, the long
bones, and the chest. Some patients have one episode every
few years, while others have many episodes per year. The crises
can be severe enough to require admission to the hospital
for pain control and intravenous fluids.
Many manifestations of this disease are a result of the
fragility and inflexibility of the sickle red blood cells.
When patients experience dehydration, infection, and low oxygen
supply, these fragile red blood cells assume a crescent shape,
causing red blood cell destruction and thickening of the blood.
Updated Date: 05/08/00
Updated by: Bradley G. Somer, MD, Division
of Hematology-Oncology, Hospital University of Pennsylvania,
Verimed Health Network
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