Genetic Testing Disease Risk Profiling Sickle Cell Anemia

Sickle cell anemia is a chronic, inherited blood disease that is characterized by anemia (a disorder marked by low levels of healthy red blood cells) and pain. The shape of hemoglobin molecules is mutated so they assemble into long rod shapes that resemble sickles.

These deformed clumps inhibit blood from flowing through capillaries. This keeps blood from going into various tissues and results in pain and tissue damage. The blood cells also have shorter life spans and are not replaced frequently enough so the patient becomes anemic.

Early diagnosis is critical since treatment can ensure a somewhat normal life. A simple blood test is performed on newborn babies to identify sickle cell anemia genes. This blood test identifies the disease. This is later confirmed with a second blood test. The test also identifies carriers of the gene who have one copy of the sickle cell anemia DNA.

Symptoms of Sickle Cell Anemia

Symptoms vary greatly between patients. Some have mild symptoms with periods of pain and various other complications. Others have severe symptoms. Life expectancy is usually shortened. On average, males with sickle cell anemia live until age 42 and females live until age 48.

Symptoms and conditions associated with sickle cell anemia include:

  • Anemia: General symptoms include paleness, shortness of breath and fatigue. Pain in joints and organs, eye problems and yellowing of the skin are also frequent symptoms. Shortage of red blood cells causes delayed growth as well.
  • Dactylitis, or “hand-foot syndrome”: This condition occurs when blood cannot flow to the hands and feet, resulting in pain, swelling and fever.
  • Vaso-occlusive crisis: This symptom manifests itself when the sickle-shaped cells do not allow blood to flow to certain tissues and organs, causing pain and organ damage.

Individuals with sickle cell anemia are susceptible to certain complications and are more likely to get infections. Strokes are common, especially in children. Acute chest syndrome, similar to pneumonia, is characterized by chest pain, fever, difficulty breathing and an abnormal chest X-ray.

Sickle Cell Anemia Inheritance

People with ancestors in sub-Saharan Africa have a higher probability of inheriting sickle cell anemia. The condition also affects Spanish-speaking populations, Saudi Arabians, people from India and Mediterranean countries such as Turkey, Greece and Italy. About one in 500 African-Americans and one in 1000 Hispanic-Americans have sickle cell anemia. About one in 12 African-Americans is a carrier of the disease.

The sickle cell anemia DNA sequence has a mutated hemoglobin gene. Sickle cell anemia is an autosomal recessive disease. A person must have two mutated HBB genes, which provide code for hemoglobin, in order to display the disease. Those who have one or more of the alleles that cause it are resistant to malaria. This is a survival adaptation since the clumping of the cells is not compatible with malaria.

Treating Sickle Cell Anemia

No cure exists for sickle cell anemia. When a painful episode occurs, painkillers and hydration are the main treatments. Opioids or nonsteroidal anti-inflammatory drugs may also be introduced to the system, depending on the level of pain.

Blood transfusions correct the decrease in red blood cells and help make the situation less life-threatening in children. Penicillin taken from two months to five years of age prevents infection from pneumococcal bacteria. The anticancer drug hydroxyurea has been found to reduce painful episodes and acute chest syndrome.

Resources

Oak Ridge National Laboratory (2005). Genetic disease profile: sickle cell anemia. Retrieved September 21, 2008, from the Oak Ridge National Laboratory Web site: http://www.ornl.gov/sci/techresources/Human_Genome/posters/chromosome/sca.shtml.