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Sickle cell disease (also known as sickle cell anemia) is a blood disorder that causes red blood cells to be formed into a crescent shape, which results in decreased blood flow and oxygenation. People with sickle cell disease usually experience chronic pain and fatigue.
Sickle Cell Disease falls under theCardiovascular Healthcategory.
Last Updated:July 6, 2023
Sickle cell disease (SCD) refers to a group of inherited health conditions characterized by the presence of atypical hemoglobin molecules. Hemoglobin is usually composed of four protein chains, two “alpha” and two “beta”. In some patients, one or both beta chains are replaced by abnormal proteins that affect their function. If a single beta chain is replaced, this is called sickle cell trait (SCT) and is not associated with health problems. Sickle cell disease results when both beta chains are affected.[1] The commonest beta chain mutation is called hemoglobin S. If both beta chains are hemoglobin S (referred to as HbSS), the condition is called sickle cell anemia.
These alterations in the hemoglobin structure cause some red blood cells to change into a sickle, or half-moon, shape.[2] Compared to normal red blood cells, sickled red blood cells have a significantly shorter lifespan of only 10 to 20 days, while normal ones live for 90 to 120 days. Additionally, the distorted shape of sickled red blood cells can lead to the blockage of blood vessels, resulting in reduced blood flow and oxygen supply to vital organs and tissues.
Although newborns can be screened for sickle cell disease (SCD) from birth, signs and symptoms typically don’t appear until 5 or 6 months of age. The type and intensity of these signs and symptoms vary among individuals and may change over time, depending on which organs are affected.[3]
SCD is characterized by the accelerated breakdown of sickled red blood cells (hemolysis), which reduces the number of circulating red blood cells, causing anemia. This decreases the oxygen supply to organs and tissues. Common symptoms of anemia include fatigue, tiredness, irritability, and in more severe cases, shortness of breath. Accelerated hemolysis can also cause jaundice (yellowing of the skin), or icterus (yellowing of the white part of the eye, also called the sclera). These are among the earliest signs of SCD.[2]
Sickled red blood cells are rigid and adhesive, which can obstruct small blood vessels. This can cause episodes of pain, known as pain crises, of varying intensity and frequency. Pain crises can affect any part of the body, but most commonly the lower back and lower extremities.[4] Reduced blood flow can also result in swollen hands and feet.[1]
Children’s growth rate and development during puberty may be impacted due to inadequate delivery of oxygen and essential nutrients to the body. Children affected by SCD are also more susceptible to frequent infections.[2]
Both sickle cell disease (SCD) and sickle cell trait (SCT) can be diagnosed before birth, after birth, or during adulthood.[1]
Prenatal tests, such as chorionic villus sampling (CVS) and amniocentesis, can confirm whether the baby will have SCD or SCT, and are typically offered to women with a higher risk of having a baby affected by a genetic condition.[5]
Diagnosis of SCD or SCT in newborns or adults can be done through a simple blood test. In the US, all states conduct newborn screening for SCD to enable early intervention if deemed necessary. Additionally, parents who are planning on having a baby can undergo a blood test to check if they carry the sickle cell gene and to understand the likelihood of their children having SCT or SCD.[1]
Bone marrow transplantation and stem cell transplantation are currently the only available cures for sickle cell disease (SCD). However, these procedures are risky, and to be successful they require a close match between the donor and recipient. Finding a suitable donor, even among relatives, can be challenging, and as a result, a bone marrow transplant is typically considered and offered only to children with severe SCD.[1]
Common medications prescribed for SCD include:[6]
Additionally, in severe cases of anemia, or in patients who have had a stroke or are at risk of developing one, blood transfusions and red blood cell transfusions may be recommended.[6]
Folic acid has long been prescribed as a supplement for SCD, despite a lack of evidence supporting its effectiveness. Folate, also known as vitamin B9, is a water-soluble vitamin involved in the production of red blood cells. It is believed that adequate intake of folic acid can alleviate anemia symptoms caused by the rapid breakdown of red blood cells in SCD patients. However, recent data analysis indicates that while supplementation with folic acid increases folate levels, it does not significantly impact hemoglobin concentration, anemia symptoms, pain crises, rate of infections, or hospitalizations.[8]
Iron deficiency is common in individuals with SCD, but there are conflicting opinions regarding supplementation with iron. On one hand, low iron levels may reduce painful crises by decreasing hemoglobin concentration in sickled red blood cells.[9] On the other hand, iron deficiency can have a detrimental impact on both physical and mental growth, making adequate levels important. Until further studies are conducted, people with SCD should consult their doctor before starting any iron supplements.
Zinc sulfate may also be a promising supplement for SCD. Studies show that it may reduce the frequency of pain crises if taken for a year, and it may reduce the number of infections after just three months of use. However, these findings are based on a small group of trials, and more studies should be conducted to verify its efficacy and safety.[10]
Additionally, research is exploring the use of L-arginine as an adjunct therapy to reduce vaso-occlusion and associated pain crises. L-arginine is required to produce nitric oxide (NO), a vasodilator. Studies show that children who received L-arginine in addition to parenteral opioids experienced a 54% reduction in total opioid use throughout the study.[11]
Children with SCD are more likely to have lower weight and body mass index (BMI). This is possibly caused by reduced appetite due to elevated inflammatory mediators, and a higher basal metabolic rate and resting energy expenditure. Inadequate nutrient intake or malnutrition may also worsen SCD signs and symptoms, so special attention to diet may be beneficial, especially during the growth phase in children and the development phase in teenagers.[12]
One study from 2016 on children between 6 months and 18 years old found that intakes of calcium, iron, vitamin C, and vitamin B1 were lower in children affected by SCD. Low intakes of proteins, lipids, and carbohydrates, and low levels of micronutrients such as calcium, vitamin B1, vitamin B2, vitamin B3, iron, and phosphorus are also correlated with more hospitalization days per year in children and teenagers.[12] Nutritional interventions, such as supplementation via nasogastric tube[13], have been studied relative to their impact on children's growth rate. Despite the positive outcomes, these procedures are not easily applicable in everyday life; more studies will hopefully be performed to find more practical interventions.
Some studies have looked into the potential of marijuana to relieve pain crises in people with SCD, although the results were not conclusive and more data is needed.[14]
Genetic therapies are also being explored, and some are being tested in clinical trials. They target the disease by either repairing a faulty gene or by adding a new genetic sequence that improves the way the cell works. No genetic therapy is currently approved by the Food and Drug Administration (FDA) for SCD, as no genetic therapy’s safety and efficacy for treatment of SCD has been established.[6]
People with SCD are encouraged to drink more and keep hydrated, as dehydration can exacerbate pain crises. Staying updated with all recommended vaccinations, including the flu vaccination, is also crucial to prevent infections.[6]
Sickle cell disease (SCD) is an inherited condition, so it’s present at birth. It occurs when a baby receives a copy of a specific mutated form of the HBB gene from both parents, which results in one or both beta globins (the beta chains of the hemoglobin molecules) being replaced by hemoglobin S. This type of gene inheritance pattern is called autosomal recessive, which means that disease happens only when both copies of the sickle cell gene are altered. This is possible only when both parents carry the mutation.[2] People born with only one copy of the altered gene don’t usually manifest any symptoms and live a healthy life, although they can still pass the defective gene to their children. This is called sickle cell trait (SCT).[reference|url=https://www.hematology.org/education/patients/anemia/sickle-cell-disease|title=Sickle Cell Disease: American Society
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