Sickle Cell Anemia

Sickle cell crisis (HgbSS) is a debilitating disorder characterized by blood cells changing into a sickle shape as a result of stressful conditions such as exhaustion, hypoxia, severe infection, or even cold temperatures. "The term sickle cell disease (SCD) is used in a generic sense to refer to all the clinically severe sickling syndromes" (Desai,Dhanani, 2002). This paper is going to describe the theoretical origin of sickle cell, the genetic components, pathophysiology of the sickle cell crisis, risk factors and demographics as well as procedures, treatments and the Psycho-Social aspect of the disease.

Sickle cell crisis occurs in people who have what is known as the Hemoglobin S gene (HbS), or more commonly the sickle cell trait. The theory is that the sickle cell trait is a characteristic that has developed to protect people from some parts of Africa and the Mediterranean from Malaria. "Malaria is a major killer of children worldwide and the strongest known force for evolutionary selection in the recent history of the human genome" (Kwiatkowski, 2005) Malaria is a disease from a parasite that mosquitoes carry and infect humans with when they are bitten. The sickle cells impair malaria growth and development. Researchers realized that where there was an endemic of malaria there was also a general population of people with the sickle cell trait (hemoglobin S gene) in the same geographical region. The researchers also saw that people from the highland regions of the African continent did not display the high expression of the sickle gene as the people that lived in the lowland regions. Malaria is not found in the highlands of Africa because of the cooler, drier climate and neither is the hemoglobin S gene, but is found in the lowlands, where there is a warmer, more humid climate there is a highly increased amount of people with the gene. The sickle trait provides a survival advantage over people with normal hemoglobin in areas where malaria is prominent. People, particularly children infected with malaria are more likely to survive the acute illness if they have the sickle cell trait.

The sickle cell trait is passed on from generation to generation. It is an autosomal recessive disorder. If one parent has the sickle trait and the other parent is normal than sickle cell is beneficial if their children end up with only one of the genes. The child with only one gene will be protected from malaria because of the sickle cell trait. Their red blood cells, containing some abnormal hemoglobin, tend to sickle when they are infected by the malaria parasite. Those infected cells flow through the spleen, which sorts them out because of their sickle shape and the parasite is eliminated along with them. If both parents have the gene it can be fatal. Two parents with the gene means that there is a one in four chance that their child can end up with two sickle genes. The child/children that end up with two sickle cell genes will have what is known as the disease, sickle cell anemia. (Wikipedia)

Sickle cell anemia is a mutation in the chain of hemoglobin; this mutation forms the hemoglobin S gene. The mutation is an absence of a polar amino acid that makes the red blood cell a sickled shape and decreases its elasticity. Low oxygen makes the red blood cells sickle. These cells fail to return to normal shape when normal oxygen tension is restored. The blood cells become rigid with each attack and cannot pass easily through the capillaries, causing ischemia.

People born with the sickle cell disease have to be careful in order to prevent a crisis. Sickle cells are already present in their blood which is a normal characteristic of the disease. The most common causes of a crisis are cold weather, strenuous activity, dehydration and infection. Cold weather causes vasoconstriction of the blood vessels causing the sickle cells to become further obstructed, decreasing the oxygen and a sickle cell crisis will usually follow. If they are overexerting themselves during exercise or any activity that will cause them to become short of breath and will increase their need for oxygen it can potentiate a crisis. Dehydration can induce a crisis because the blood becomes viscous, increasing the risk for occlusion. Some infections can precipitate a crisis such as a respiratory infection or if an infection causes the bone marrow to decrease the production of red blood cells (aplastic crisis).

There are three different crisis' that occur in the sickle cell disease; hemolytic, splenic sequestration, and aplastic. The 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 (Goldman, 2004).

Children with sickle cell anemia usually do not show symptoms till approximately 6 months of age. This is when the child's hemoglobin changes from fetal to adult form (Pillitteri, 2007, pgs 1396-1397). Initially the child will present with signs of a fever and anemia. When the red blood cells sickle, they do not move freely through vessels. This stasis of blood and infarction may occur in any body part, which will lead to local disease. Some infants have swelling of the hands and feet (a hand-foot syndrome). This is most likely caused by aseptic infarction of the bones in these areas. These children may also present with a protruding abdomen due to an enlarged spleen and liver. However, in adolescence, the spleen may be decreased from repeated infarction and atrophy. This will lead the child more susceptible to infection than normal because the spleen can no longer filter bacteria. The liver enlarges due to stasis of blood flow. This will eventually lead to cirrhosis due to infarcts and tissue scarring. The kidneys may also undergo scarring which will lead to a decrease in kidney function. The sclerae are generally icteric from the release of bilirubin. Priapism (persistent, painful erection) may occur due to cell clusters in the blood vessels of the penis. Chronic Lung Disease is a general term for a group of symptoms that arise as a result of lung damage and loss of lung tissue due to lack of blood supply. These symptoms include difficulty breathing, episodes of chest pain, and exercise intolerance (Villella, 2006).