Anemia - sickle cell; Hemoglobin SS disease
(Hb SS)
Sickle cell disease
Definition - Causes, incidence, and risk factors - Symptoms - Signs and tests - Treatment .
Definition
Sickle cell
anemia is an inherited disease in which the red blood cells, normally
disc-shaped, become crescent shaped. As a result, they function abnormally and
cause small blood clots. These clots give rise to recurrent painful episodes
called "sickle cell pain crises.
Causes, incidence, and risk factors
Sickle cell
anemia is caused by an abnormal type of hemoglobin
called hemoglobin S. Hemoglobin is a protein inside red blood cells that
carries oxygen. Hemoglobin S, however, reduces the amount of oxygen inside the
cells, distoring their shape. The fragile, sickle-shaped cells
deliver less oxygen to the body's tissues, and can break into pieces that
disrupt blood flow.
Sickle cell
anemia is inherited as an autosomal recessive trait , which means it occurs in
someone who has inherited hemoglobin S from both parents. Sickle cell disease
is much more common in certain ethnic groups, affecting approximately one out
of every 500 African Americans. Someone who inherits hemoglobin S from one
parent and normal hemoglobin (A) from the other parent 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 thalassemia.
Although sickle
cell disease is present at birth, symptoms usually don't occur until after 4
months of age. Sickle cell anemia may become life threatening . Blocked blood
vessels and damaged organs can cause acute
painful episodes, or "crises." There are several types of crises:
Hemolytic crisis
occurs when damaged red blood cells break down
Splenic sequestration crisis
is when the spleen enlarges and traps the blood cells
Aplastic crisis
results when an infection causes the bone marrow to stop producing
red blood cells
These painful
crises, which occur in almost all patients at some point in their lives, 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.
Repeated crises
can cause damage to the kidneys, lungs, bones, eyes, and central
nervous system.
Symptoms
Common symptoms
include:
paleness
yellow
eyes/skin
fatigue
breathlessness
rapid
heart rate
delayed
growth and puberty
susceptibility
to infections
ulcers
on the lower legs (in adolescents and adults)
jaundice
bone
pain
attacks
of abdominal
pain
fever
The patient may
also have:
bloody
urine (hematuria
)
frequent
urination
excessive
thirst
painful
erection (priapism;
this occurs in 10-40% of men with the disease)
chest
pain
poor
eyesight/blindness
Signs and tests
Tests commonly
performed to diagnose and monitor patients with sickle cell anemia include:
Complete
blood count (CBC
)
Hemoglobin
electrophoresis
Sickle
cell test
Patients with
sickle cell may have abnormal results on certain tests, as follows:
peripheral
smear displaying sickle cells
urinary
casts or blood in the urine
Hemoglobin;
serum decreased
elevated
bilirubin
high
white blood cell count
elevated
serum potassium
elevated
serum creatinine
blood
oxygen saturation may be decreased
CT
scan or MRI can display strokes in certain circumstances
Treatment
Patients with
sickle cell disease need continous treatment, even when they are not
having a painful crisis. Supplementation with folic acid,
an essential element in producing cells, is required because of the rapid red
blood cell turnover.
The purpose of
therapy is to manage and control symptoms and to try to limit the frequency of
crises.
During a sickle
crisis, certain therapies may be necessary. Painful episodes are treated with analgesics
and adequate liquid intake. Treatment of pain is critical. Non-narcotic
medications may be effective, but some patients will require narcotics.
Hydroxyurea
(Hydrea) was found to help some patients by reducing the frequency of painful
crises and episodes of acute chest syndrome and decreasing the need for blood
transfusions. There has been some concern about the possibility of this drug
causing leukemia, but as yet there are no definitive data that Hydrea causes
leukemia in sickle cell patients.
Newer drugs are
being developed to manage sickle cell anemia. Some of these agents work by
trying to induce the body to produce more fetal hemoglobin (therefore
decreasing the amount of sickling) or by increasing the binding of oxygen to
sickle cells. But as yet, there are no other widely used drugs that are
available for treatment.
Bone marrow
transplants can be curative, this therapy is indicated in only a minority of
patients, predominantly because of the high risk of the procedure (the drugs
needed to make the transplant possible are highly toxic) and difficulty in
finding suitable donors. Also, bone marrow transplants are much more
expensive than other treatments.
Antibiotics and
vaccines are given to prevent bacteria infections, which are common in
children with sickle cell disease.
Additional
treatments may include:
partial
exchange transfusion for acute chest syndrome
transfusions
or surgery for neurological events, such as strokes
dialysis
or kidney transplant for kidney disease
irrigation
or surgery for priapism
surgery
for eye problems
hip
replacement for avascular necrosis of the hip (death of the joint)
gallbladder
removal (if there is significant gallstone disease)
wound
care, zinc oxide, or surgery for leg ulcers
drug
rehabilitation and counseling for the psychosocial complications
