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Sickle cell disease
Sickle cell disease, or sickle cell anemia, is an inherited genetic disease of the blood
Sickle cell disease, also known as sickle cell anemia, is an inherited genetic disease that affects the blood. Sickle cell disease, along with thalassemia, is part of diseases called hemoglobinopathies. These diseases affect hemoglobin, which is a protein responsible for oxygen transport in red blood cells.
In healthy people, red blood cells are round and flexible, allowing them to transport oxygen through blood vessels easily, while in people affected by sickle cell disease, these globules adopt a sickle or crescent shape and become more rigid, clogging small blood vessels and reducing the flow of blood and oxygen to the body.
This can lead to symptoms in both adults and children, including:
- Anemia: feeling of fatigue or lack of energy caused by an insufficient number of red blood cells that transport oxygen to the body.
- Pain: usually in the chest, abdomen, and joints–as a result of the obstruction caused by sickle-shaped red blood cells in the blood vessels.
- Swelling of the hands and feet.
- Jaundice: yellowing of the skin and eyes when the disease affects liver function.
- Infections: caused by the involvement of the spleen, an organ whose function is to fight infections.
- Growth retardation: related to the shortage of red blood cells, which provide oxygen and nutrients necessary for the development of the body.
The treatment of sickle cell disease usually consists of increased fluid intake, healthy diet, taking folic acid supplements, using analgesics, vaccines, and antibiotics to prevent and treat infections, and other methods to control the symptoms.
Bone marrow transplantation is currently the only effective treatment. However, it is not suited for every patient, as the risks involved may be a reason to discourage this kind of therapy.
Recent advances in stem cell research have shown potential for gene therapy as a treatment option for sickle cell disease in the future.
The development of sickle cell disease is associated with mutations in the HBB gene, which is located on chromosome 11. EThis gene provides instructions for the production of beta hemoglobin; therefore, any change (the presence of a mutation) in these instructions results in a protein product that is functionally defective.
The most common mutation is an adenine-to-thymine substitution at position 14 of the HBB gene. This change results in a protein change of a glutamic acid (Glu) for valine (Val) at position 6, producing a type of hemoglobin known as hemoglobin S.
Sickle cell disease is one of the most common genetic diseases worldwide, affecting approximately 50 million people. It is the most prevalent in intertropical Africa, although it is also present in the European Mediterranean, the Middle East, and India.
It appears that this high frequency and geographical distribution is caused by the fact that the p.Glu6Val mutation gives its carriers greater resistance to malaria, consequently leading to a their higher survival rate in regions where malaria is endemic.
Sickle cell disease follows an autosomal recessive inheritance pattern, which means that both copies of the gene, one inherited from the father and one from the mother, must be altered for the disease to develop. People with only one altered if the gene are carriers of the disease and can pass the altered copy to their offspring, but they themselves do not develop it.
As indicated by the World Health Organization (WHO), prevention is an appropriate strategy to avoid the onset of the disease, which can start with genetic testing, currently recommended for individuals who are at risk of passing the disease to their children.
These screening tests can be done before pregnancy through a preconception consultation. During genetic counseling that accompanies this type of analysis, the specialist informs parents of the probability of transmitting the disease to their children, the treatments they would need, and the options available to avoid transmission.