Part 1 of 8: Overview

What Is Sickle Cell Anemia?

Sickle cell anemia, or sickle cell disease (SCD), is a genetic disease of the red blood cells (RBCs). Normally RBCs are shaped like discs, which gives them the flexibility to travel through even the smallest blood vessels. However, with this disease, the RBCs have an abnormal crescent (“sickle”) shape. This makes them sticky and rigid. They can get trapped in small vessels and block blood from reaching different parts of the body. This can cause pain and tissue damage.

SCD is an autosomal recessive condition. You need two copies of the gene to have the disease. If you have only one copy of the gene, you are said to have sickle cell trait.


Part 2 of 8: Symptoms

What Are the Symptoms of Sickle Cell Anemia?


Symptoms of sickle cell anemia usually show up at a young age. They may appear in babies as early as 4 months old, but generally occur around the 6-month mark.

While there are multiple types of SCD, they all have similar symptoms at different levels of severity. These include:

  • excessive fatigue or irritability (from anemia)
  • fussiness (in babies)
  • bedwetting (from associated kidney problems)
  • jaundice (yellowing of the eyes and skin)
  • swelling and pain in hands and feet
  • frequent infections
  • chest pain

Part 3 of 8: Types

What Are the Types of Sickle Cell Disease?

 Type 1

Hemoglobin is the protein in RBCs that carries oxygen. It normally has two alpha chains and two beta chains. The four main types of sickle cell anemia are caused by different mutations in these genes.

Hemoglobin SS Disease

Hemoglobin SS disease is the most common type of sickle cell disease. It occurs when you inherit copies of the hemoglobin S gene from both parents. This forms hemoglobin known as Hb SS. As the most severe form of SCD, individuals with this form also experience the worst symptoms at a higher rate.

Hemoglobin SC Disease

Hemoglobin SC disease is the second most common type of sickle cell disease. It occurs when you inherit the Hb C gene from one parent and the Hb S gene from the other. Individuals with Hb SC have similar symptoms to individuals with Hb SS. However, the anemia is less severe.

Hemoglobin SB+ (Beta) Thalassemia

Hemoglobin SB+ (beta) thalassemia affects beta globin gene production. The size of the red blood cell is reduced because less beta protein is made. If inherited with the Hb S gene, you will have Hemoglobin S Beta thalassemia. Symptoms are not as severe.

Beta-Zero Thalassemia

Beta-zero thalassemia is the second type of beta thalassemia. It has similar symptoms to Hb SS anemia. However, sometimes the symptoms of beta-zero thalassemia are more severe. It is associated with a poorer prognosis.

People who only inherit a mutated gene from only one parent are said to have sickle cell trait. They may have no symptoms or reduced symptoms.


Part 4 of 8: Risk Factors

Who Is at Risk for Sickle Cell Anemia?

Risk Factors

Children are only at risk for sickle cell if both parents carry sickle cell trait. A blood test

called a hemoglobin electrophoresis can also determine which type you might carry.

People from regions that have endemic malaria are more likely to be carriers. This includes people from:

  • Africa
  • India
  • the Mediterranean
  • Saudi Arabia

Part 5 of 8: Complications

What Complications Can Arise from Sickle Cell Anemia?


SCD can cause severe complications. These complications appear when the sickle cells block vessels in different areas of the body. Painful or damaging blockages are called sickle cell crises.

Severe Anemia

Anemia is a shortage of RBCs. Sickle cells are easily broken. This breaking apart of RBCs is called chronic hemolysis. RBCs generally live for about 120 days. Sickle cells live for a maximum of 10 to 20 days.

Hand-Foot Syndrome

Hand-Foot Syndrome occurs when sickle-shaped RBCs block blood vessels in the hands or feet. This causes the hands and feet to swell. It can also cause leg ulcers. Swollen hands and feet are often the first sign of sickle cell anemia in babies.

Splenic Sequestration

Splenic sequestration is a blockage of the splenic vessels by sickle cells. It causes a sudden, painful enlargement of the spleen.

Delayed Growth

Delayed growth often occurs in people with SCD. Children are generally shorter but regain their height by adulthood. Sexual maturation may also be delayed. This happens because sickle cell RBCs can’t supply enough oxygen and nutrients.

Neurological complications include seizures, bleeding in the brain, or even coma. They are caused by brain blockages. Immediate treatment should be sought.

Eye Problems

Blindness is caused by blockages in the vessels supplying the eyes. This can damage the retina.

Skin Ulcers

Skin ulcers in the legs can occur if small vessels there are blocked.

Heart Disease and Chest Syndrome

Since SCD interferes with blood oxygen supply, it affects the blood vessels. Over time, this can lead to an enlarged heart and subsequent heart disease. This can also lead to pain known as chest syndrome. High blood pressure (hypertension) and stroke may also develop.


Priapism is a lingering, painful erection that can be seen in some men with sickle cell. This happens when the blood vessels in the penis are blocked. It can lead to impotence if left untreated.


Gallstones are one complication not caused by a vessel blockage. Instead, they are caused by the breakdown of RBCs. A byproduct of this breakdown is bilirubin. High levels of bilirubin can lead to gallstones. These are also called pigment stones.


Part 6 of 8: Diagnosis

How Is Sickle Cell Anemia Diagnosed?


All newborns in the United States are screened for sickle cell disease. Prebirth testing looks for the sickle cell gene in your amniotic fluid.

In children and adults, one or more of the following procedures may also be used to diagnose sickle cell.

Detailed Patient History

This condition often first appears as acute pain in the hands and feet. Patients may also have:

  • severe pain in the bones
  • anemia
  • painful enlargement of the spleen
  • growth problems
  • respiratory infections
  • ulcers of the legs
  • heart problems

Your doctor may want to test you for sickle cell anemia if you have any of the symptoms mentioned above.

Blood Tests

Several blood tests can be used to look for SCD:

  • blood counts can reveal an abnormal Hb level in the range of 6 to 8 g/dL
  • blood films may show RBCs that appear as irregularly contracted cells
  • sickle solubility tests look for the presence of Hb S

Hb Electrophoresis

Hb electrophoresis is always needed to confirm the diagnosis of sickle cell. It measures the different types of hemoglobin in the blood.

Part 7 of 8: Treatments

How Is Sickle Cell Anemia Treated?


A number of different treatments are available for SCD:

  • Antibiotics like penicillin may be given from 2 months of age to 5 years. They help prevent pneumonia in sickle cell patients.
  • Supplemental oxygen is given through a mask. It makes breathing easier and improves oxygen levels in the blood.
  • Pain medication is used to relieve the pain during a sickle crisis. You may need over-the-counter drugs or strong prescription pain medication like morphine.
  • Hydroxyurea (Droxia, Hydrea) helps to increase production of fetal hemoglobin. It may reduce the number of blood transfusions.
  • Immunizations can help prevent infections. Patients tend to have lower immunity.
  • Surgery may be used to treat persistent and painful erections.

Bone marrow transplant has been used to treat sickle cell anemia. Children younger than 16 years of age who have severe complications and have a matching donor are the best candidates.

Blood transfusions can also treat sickle cell anemia. Packed red cells are removed from donated blood and given to patients. This improves transport of oxygen and nutrients.

Home Care

There are things you can do at home to help your sickle cell symptoms:

  • Use heating pads for pain relief.
  • Take folic acid supplements, as recommended by your doctor.
  • Adequate fruits, vegetables, and whole-wheat grains are important and can help your body make more RBCs.
  • Drink more water to reduce the chances of sickle cell crises.
  • Exercise regularly and reduce stress to reduce crises, too.

Support groups can also help you deal with this condition.


Part 8 of 8: Long-Term Outlook

What Are the Long-Term Outcomes of Sickle Cell Disease?


The prognosis of the disease varies. Some patients have frequent and painful sickle cell crises. Others only rarely have attacks.

Sickle cell anemia is an inherited disease. Talk to a genetic counselor if you are worried that you might be a carrier. This can help you understand possible treatments, preventive measures, and reproductive options.

Our Cells Road Map

Sickle Cell and Haemoglobin Illnesses

Sickle-cell disease and other
haemoglobin disorders

Fact sheet N°308
January 2011

Key facts

Approximately 5% of the world’s population
carries trait genes for haemoglobin
disorders, mainly, sickle-cell disease and
Haemoglobin disorders are genetic blood
diseases due to inheritance of mutant
haemoglobin genes from both, generally
healthy, parents.
Over 300 000 babies with severe
haemoglobin disorders are born each year.
The health burden of haemoglobin disorders
can be effectively reduced through
management and prevention programmes.

What are haemoglobin disorders?

Haemoglobin disorders are inherited blood
diseases that affect how oxygen is carried in the
body. Haemoglobin disorders fall into two main
categories: sickle-cell disease and

Sickle-cell disease is characterized by a
modification in the shape of the red blood
cell from a smooth, donut-shape into a
crescent or half moon shape. The
misshapen cells lack plasticity and can
block small blood vessels, impairing blood
flow. This condition leads to shortened red
blood cell survival, and subsequent anaemia,
often called sickle-cell anaemia. Poor blood
oxygen levels and blood vessel blockages in
people with sickle-cell disease can lead to
chronic acute pain syndromes, severe
bacterial infections, and necrosis (tissue
Thalassaemias are also inherited blood
disorders. People with thalassaemia are not
able to make enough haemoglobin, which is
found in red blood cells. When there is not
enough haemoglobin in the red blood cells,
oxygen cannot get to all parts of the body.
Organs then become starved for oxygen and
are unable to function properly. There are
two major types of thalassaemia, alpha and
beta, which are named for the two protein
chains that make up normal haemoglobin.
Alpha and beta thalassaemia have both mild
and severe forms.

Facts about haemoglobin disorders

It is estimated that each year over 300 000
babies with severe forms of these diseases
are born worldwide, the majority in low and
middle income countries.
Approximately 5% of the world’s population
are healthy carriers of a gene for sickle-cell
disease or thalassaemia. The percentage of
people who are carriers of the gene is as
high as 25% in some regions.
These conditions are most prevalent in
tropical regions; however population
migration has spread these diseases to most
Thalassaemias are the most common in
Asia, the Mediterranean basin, and the
Middle East.
Sickle-cell disease predominates in Africa.

What causes haemoglobin disorders?

Haemoglobin disorders are inherited from
parents in much the same way as blood type,
hair colour and texture, eye colour and other
physical traits.

Sickle-cell disease and severe forms of
thalassaemia (thalassaemia major) can occur
only when both parents are carriers of trait
genes for the particular condition. A child who
inherits two of the same trait genes - one from
each parent - will be born with the disease.
However, a child of two carriers has only a 25%
chance of receiving two trait genes and
developing the disease, and a 50% chance of
being a carrier. Most carriers lead completely
normal, healthy lives.

How can haemoglobin disorders be

Haemoglobin disorders can be effectively
reduced through a strategic balance of disease
management and prevention programmes.

Sickle-cell disease can be managed by simple
procedures including:

high fluid intake
healthy diet
folic acid supplementation
pain medication
vaccination and antibiotics for the
prevention and treatment of infections
a number of other therapeutic measures.

Thalassaemia major requires regular blood
transfusions to maintain an adequate supply of
haemoglobin and sustain life. As a result of
multiple transfusions, organs become severely
overloaded with iron and a specific treatment is
needed to manage this condition.
Thalassaemias can be cured by a successful
bone-marrow transplant, however this
procedure is expensive and not readily available
in most settings. Recently, gene therapy has
been successfully applied to a patient with

The most cost-effective strategy for reducing
the burden of haemoglobin disorders is to
complement disease management with
prevention programmes. Inexpensive and
reliable blood tests can identify couples at risk
for having affected children. This screening is
especially opportune before marriage or
pregnancy, allowing couples to discuss the
health of their family. Subsequent genetic
counselling informs trait carriers of risks that
the condition may be passed along to their
children, the treatment needed, if affected by a
haemoglobin disorder, and the possible options
for the couple. Prenatal screening of genetic
diseases raises specific ethical, legal and social
issues that require appropriate consideration.

WHO response

The governing bodies of WHO have adopted two
resolutions on haemoglobin disorders. The
resolution on sickle-cell disease from the 59th
World Health Assembly in May 2006 and the
resolution on thalassaemia from the 118th
meeting of the WHO Executive Board call upon
affected countries and the Secretariat of WHO to
strengthen their response to these conditions.
In addition, a resolution on the prevention and
management of birth defects, including sickle-cell disease and thalassaemias, was adopted by
the 63rd World Health Assembly in May 2010.

Specifically, WHO will:

increase awareness of the international
community of the global burden of these
promote equitable access to health services;
provide technical support to countries for the
prevention and management of these
disorders; and
promote and support research to improve
quality of life for those affected.


Sickle cell anemia is an inherited form of anemia — a condition in which there aren't enough healthy red blood cells to carry adequate oxygen throughout your body.

Normally, your red blood cells are flexible and round, moving easily through your blood vessels. In sickle cell anemia, the red blood cells become rigid and sticky and are shaped like sickles or crescent moons. These irregularly shaped cells can get stuck in small blood vessels, which can slow or block blood flow and oxygen to parts of the body.

There's no cure for most people with sickle cell anemia. However, treatments can relieve pain and help prevent further problems associated with sickle cell anemia.

Facts About Sickle Cell Disease

Three girls in a pyramidSCD is a group of inherited red blood cell disorders. Healthy red blood cells are round, and they move through small blood vessels to carry oxygen to all parts of the body. In someone who has SCD, the red blood cells become hard and sticky and look like a C-shaped farm tool called a “sickle”. The sickle cells die early, which causes a constant shortage of red blood cells. Also, when they travel through small blood vessels, they get stuck and clog the blood flow. This can cause pain and other serious problems such infection, acute chest syndrome and stroke.


Types of SCD


Following are the most common types of SCD:


People who have this form of SCD inherit two sickle cell genes (“S”), one from each parent. This is commonly called sickle cell anemia and is usually the most severe form of the disease.


People who have this form of SCD inherit a sickle cell gene (“S”) from one parent and from the other parent a gene for an abnormal hemoglobin called “C”. Hemoglobin is a protein that allows red blood cells to carry oxygen to all parts of the body. This is usually a milder form of SCD.

Sickle Cell Disease
Fact Sheet

 Cell Disease Fact Sheet

View and print » Adobe PDF file

HbS beta thalassemia

People who have this form of SCD inherit one sickle cell gene (“S”) from one parent and one gene for beta thalassemia, another type of anemia, from the other parent. There are two types of beta thalassemia: “0” and “+”. Those with HbS beta 0-thalassemia usually have a severe form of SCD. People with HbS beta +-thalassemia tend to have a milder form of SCD.

There also are a few rare types of SCD:

HbSD, HbSE, and HbSO

People who have these forms of SCD inherit one sickle cell gene (“S”) and one gene from an abnormal type of hemoglobin (“D”, “E”, or “O”). Hemoglobin is a protein that allows red blood cells to carry oxygen to all parts of the body. The severity of these rarer types of SCD varies. 


Sickle Cell Trait (SCT)



People who have SCT inherit one sickle cell gene (“S”) from one parent and one normal gene (“A”) from the other parent. This is called sickle cell trait(SCT). People with SCT usually do not have any of the signs of the disease and live a normal life, but they can pass the trait on to their children. Additionally, there are a few, uncommon health problems that may potentially be related to sickle cell trait.