Sickle cell disease

Sickle cell disease is an inherited blood disorder. People with this disease have an abnormality in the hemoglobin molecules, which are located in the red blood cells. Someone has sickle cell disease when they inherit a certain abnormality in the gene for hemoglobin from both parents. Due to this abnormality, the red blood cell deforms when it does not bind enough oxygen and takes on the shape of a sickle. The symptoms often appear from the sixth month of life. Someone can also suddenly have an attack, also called a sickle cell crisis. The arms, legs, hands and feet may swell and hurt severely. In addition, a person may experience severe pain in the upper abdomen or shortness of breath.

Hemoglobin

Hemoglobin is a protein found in human red blood cells. The molecule is able to bind and transport oxygen or carbon dioxide. The hemoglobin molecules in a red blood cell absorb oxygen in the lungs. The red blood cell transports oxygen to the various tissues of our body, where it leaves the red blood cell. The tissues produce carbon dioxide, which can then bind to the hemoglobin. This is then transported back to the lungs, where we exhale the carbon dioxide again. In sickle cell disease there is an abnormality of the hemoglobin molecules, namely a point mutation of glutamic acid to valine on the beta chain of the molecule. This mutation causes red blood cells to clump together easily when there is little oxygen present. This can cause them to get stuck in small capillaries.

Sickle cell gene carrier

Everyone gets a zero for hemoglobin from both their father and mother. Sickle cell disease is an autosomal recessive disorder. This means that if someone inherits a mutated hemoglobin gene from both parents, that person will develop sickle cell disease. Both parents are then carriers of the sickle cell gene. Carriers themselves usually have no symptoms of the disease. Carrier status is fairly common among people from African countries, but also among people from the Middle East and people of Indian or Mediterranean descent, around 7 – 8%. This is because having an abnormal hemoglobin molecule protects against getting malaria. The malaria parasite cannot multiply properly in red blood cells with abnormal hemoglobin. Therefore, in areas where malaria is common, it is an evolutionary advantage and the gene is relatively common in these areas.

Symptoms

Characteristic of sickle cell disease is chronic anemia. Sickle cells have a shorter lifespan than normal red blood cells. In addition, sickle cell disease can cause life-threatening crises. Due to the abnormalities in the hemoglobin, the red blood cells easily clump together and can get stuck in the small capillaries. This is often accompanied by severe pain or dysfunction of the organ in question. The pain is especially often present in the bones of the arms, legs, feet and hands and in the abdomen. Shortness of breath may also occur if the lungs are affected. This means that organs may not receive enough blood supply, which can cause them to become damaged. A crisis can be provoked by low oxygen concentrations, for example at high altitudes, fever, hypothermia and dehydration. Children with sickle cell disease are also at risk of dangerous infections because spleen function is disrupted by sickling of red blood cells in the spleen. The symptoms usually arise around the sixth month of life, because during this period the fetal hemoglobin, which works well, is slowly replaced by the hemoglobin molecules that adults have.

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