Sickle Cell Anemia and Other Hemoglobin Disorders

You may have heard the terms sickle cell anemia or sickle cell trait or carrier.  You may also know what sickle cell anemia is – a blood disorder that causes the red blood cells to ‘sickle’ or change from a circular shape into a crescent shape.  But there are many other abnormal types of hemoglobin, and your ethnicity and family history can help you determine your risk of medical complications, as well as those of your children.

Sickle Cell Disease
Sickle cell disease (SS) is a blood disorder that affects the production of red blood cells.  Normally, hemoglobin in the red blood cells carries oxygen from the lungs to the rest of the body.  In individuals with sickle cell disease the red blood cells do not live as long as normal red blood cells.  The red blood cells can change into a sickle (crescent) shape.  When that happens, the red blood cells become stiff and cannot pass through small blood vessels.  If there is a decrease in blood flow to certain areas of the body the affected cells can become damaged.  This can cause painful sickle crises and can permanently damage organs such as the spleen, kidneys and liver.  Damage to the spleen makes individuals susceptible to certain bacterial infections.  The kidneys may become enlarged, and have decreased function.  The liver is susceptible to iron overload from multiple blood transfusions, leading to cirrhosis.  The kidneys and liver may fail after repeated damage from sickle crises over time. 

Treatment for sickle cell anemia includes early diagnosis by newborn screening, keeping up to date on vaccinations including pneumonia, extra folic acid, and prophylactic penicillin to reduce the chance of infections.  Blood transfusions help reduce the frequency of sickle crises and stroke but can cause iron overload if patients are not appropriately monitored.  Hydroxyurea is a medication that can reduce the number of painful sickle crises and occurrences of acute chest syndrome (ACS), a significant cause of morbidity and mortality with sickle cell disease.  ACS is similar to pneumonia, and is caused by an infection, or by sickled cells being trapped in the lungs.  Symptoms of ACS include chest pain and fever.  Over time, it can lead to high blood pressure due to damage to small blood vessels in the lungs, which cause the heart to pump harder to push blood through the lungs. 

One of the most significant problems in children with sickle cell anemia is stroke.  Early detection of damage to the arteries in the brain via head ultrasound using Doppler imaging of blood flow should be used once a year in children age 2 years and over.  An exchange blood transfusion can reduce the incidence of stroke.

Sickle Trait

Individuals with sickle trait are carriers, meaning they each carry one gene for sickle cell disease, and are generally healthy.  Sickle cell anemia is inherited in an autosomal recessive manner.  This means that both parents must be carriers for a child to be affected.  For a couple who are both carriers, there is a 25% risk, or one in four chance, for each of their children to be affected.  It is important for you to have a blood test and know if you have a hemoglobin trait so you are aware of the risk of having a child with sickle cell disease. This risk is independent for each child.  Individuals who are from India, or are of African, South American, Cuban, or Central American descent as well as those from Mediterranean countries such as Turkey, Greece, and Italy have the highest chance to be a carrier.  About 1 in 12 African-Americans are carriers for sickle cell trait. 

Other Hemoglobin Disorders
Missouri began screening all newborns in May of 1989 for sickle cell disease.  Through this screening, by hemoglobin electrophoresis, other abnormal hemoglobins are identified as well.  Depending on the type of problem, the hemoglobin can be abnormal in amount (decreased) or structure.  Hemoglobin C is more common in individuals from West Africa, the Mediterranean and the Middle East.  Hemoglobin SC disease (one sickle gene (S) change and one C gene change) as well as Hemoglobin S Beta Thalassemia cause symptoms that include severe anemia, recurrent painful crises, and increased risk for infections with Streptococcus pneumoniae, Hemophilus influenzae, Salmonella, and Mycoplasma peumoniae.  Individuals with SC disease often have large spleens that do not function normally and may have more problems with retinal disease than individuals with SS disease.  Individuals with Hemoglobin S Beta 0 thalassemia have symptoms similar to sickle cell disease to include anemia, enlarged spleens and bony changes including osteonecrosis, or death of the cells that make up the bones.  This can lead to enlarged or abnormally shaped bones and acute or chronic pain.

There are many other disorders of hemoglobin production and function.  A specific diagnosis is needed to determine and treat the most likely complications.  It is very important for individuals, especially children, to see physicians who are familiar with hemoglobin disorders on a regular basis.  Many of the complications can be prevented or minimized with comprehensive preventative care. 

For More Information:

American Family Physician Article September 15, 2000
GeneClinics
Learn.Genetics at the University of Utah
Missouri Department of Health and Senior Services
National Heart Lung and Blood Institute