Sickle cell Anaemia: Types, Causes, Treatment, Genetics, Diagnosis, Symptoms

Edited By Irshad Anwar | Updated on Jul 02, 2025 06:18 PM IST

Definition Of Sickle Cell Anaemia

Sickle cell anaemia is a blood disorder inherited from genes, wherein an abnormal form of haemoglobin, popularly known as sickle haemoglobin, develops in red blood cells. This abnormality due to haemoglobin confers rigidity and shape more resembling that of a sickle to the red blood cells, which can cause a variable range of health problems. The process affects persons of African, Mediterranean, Middle Eastern, and Indian ancestry, although it can also be seen in other populations.

This Story also Contains

Definition Of Sickle Cell Anaemia
Historical Background
Causes Of Sickle Cell Anaemia
Symptoms Of Sickle Cell Anaemia
Diagnosis Of Sickle Cell Anaemia
Treatment Of Sickle Cell Anaemia
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Sickle cell Anaemia: Types, Causes, Treatment, Genetics, Diagnosis, Symptoms

One should understand the genetic condition known as sickle cell anaemia because it is a lifelong illness that causes a lot of discomfort and poor quality of life. Early diagnosis and proper management could reduce suffering and potential complications. Awareness dissemination and research are very essential for the discovery of better treatment options and, finally, a cure for this killer disease.

Historical Background

Sickle cell anaemia was first described in Western literature by Dr James B. Herrick in 1910. It was based on the observation of these peculiar sickle-shaped cells in one of his patients suffering from a severe case of anaemia. Since that time, the genetic mutation for the disease has been identified and the pattern of its inheritance explained—important milestones from which this entire understanding truly began.

The progress of research into sickle cell anaemia has been immense. From very humble beginnings, where treatment options were few and prognosis was very poor, medical science has generally provided much better prognosis for these patients with new medications, transfusion programs, and newer techniques of bone marrow transplantation. Gene therapy is one of the new treatments under trial at present that shows great promise for the future.

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Causes Of Sickle Cell Anaemia

Sickle cell anaemia is caused by a specific genetic mutation in the HBB gene that codes for the beta-globin subunit of haemoglobin. The consequence is that at position six of the beta-globin chain, valine replaces glutamic acid. This seemingly minor change makes haemoglobin molecules in circumstances when they are deoxygenated stick and polymerise—forming long, rigid rods that bend red blood cells into their characteristic sickle shape.

Genetic Basis

The mutation in the HBB gene is inherited in an autosomal recessive pattern, meaning that the person should inherit two copies of the mutated gene—one copy from each parent—for the disease to ensue. Individuals bearing one mutated gene are typically asymptomatic carriers of the sickle cell trait and can transmit this gene to their children.

Molecular Mechanism

The mutation in haemoglobin resulted in haemoglobin S, which influences the red blood cells to become rigid and relatively inflexible. When the concentration of oxygen falls below a certain level, haemoglobin S polymerises, eventually making the red blood cells take a sickle shape. These crescent-shaped cells can easily break apart, sometimes obstructing narrow blood vessels, thereby producing pain and organ failure.

Symptoms Of Sickle Cell Anaemia

The symptoms of sickle cell anaemia can range from mild to severe. Chronic pain, fatigue, and anaemia are among the most common symptoms. Pain crises, also called vaso-occlusive crises, form the hallmark of the disease and occur when sickled red blood cells obstruct blood flow to tissues, leading to severe pain and potential organ damage.

Diagnosis Of Sickle Cell Anaemia

Diagnosis of sickle cell anaemia is done by screening and diagnostic tests. These include:

Screening Tests

Newborn screening programs: Many countries are rapidly instituting them to diagnose sickle cell disease early in infants.

Diagnostic Tests

Blood tests: (a) Complete blood count, or CBC, can detect anemia, and, (b) Blood smear for examining the shape of red blood cells.
Haemoglobin electrophoresis: This test detects different types of haemoglobin in blood.
Genetic testing: It confirms the presence of HBB gene mutation.

Treatment Of Sickle Cell Anaemia

Sickle cell anaemia is managed by a comprehensive way of alleviating the symptoms and preventing complications, improving the quality of life of the patient.

Medications

Hydroxyurea is a medication that increases the production of fetal haemoglobin, thereby reducing the sickling of red blood cells, which may reduce the frequency of pain crises and the need for blood transfusions. Other pain medications are also essential to help manage chronic and acute pain related to the disease.

Blood Transfusions

Regular blood transfusions in cases with severe anaemia may prevent complications like stroke. Blood transfusions can increase the number of normal red blood cells, thereby reducing the proportion of sickle cells in circulation.

Bone Marrow Transplant

Bone marrow or stem cell transplant is the only possible cure for sickle cell anaemia. It involves replacing the patient's diseased bone marrow with healthy donor marrow. It has a higher success rate in young patients and where compatible donors are available.

Lifestyle And Home Remedies

The patients are warned about observing fluid intake, good nutrition, and keeping away from factors that trigger painful crises, such as very high or low temperatures and high altitudes. To be safe from infections and ensure the disease is treated properly, regular medical checkups and vaccinations should also be sought.

Conclusion

Sickle cell anaemia is, after all, a multi-factorial genetic disorder; thus, diagnosis and management must be holistic. Awareness should be increased, and early diagnoses made to reduce the impact of the disease, to improve patient outcomes. Further efforts into finding new treatments and, optimally, a cure have to be pursued to give hope to those affected by the condition.

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Frequently Asked Questions (FAQs)

1. What is sickle cell anemia?

Sickle cell anaemia is a blood disorder caused by genetics wherein abnormally shaped red blood cells are formed.

2. What is sickle cell anemia?

Sickle cell anemia is a genetic blood disorder characterized by abnormal, crescent-shaped red blood cells. These sickle-shaped cells can block blood flow, causing pain and organ damage, and they have a shorter lifespan than normal red blood cells, leading to anemia.

3. What causes sickle cell anemia?

This happens when there is a mutation in the HBB gene that leads to producing abnormal haemoglobin, thereby resulting in red blood cells that are sickle-shaped.

4. What are the symptoms of sickle cell anaemia?

Common symptoms are chronic pain, fatigue, anaemia, and also involving complications like strokes and acute chest syndrome.

5. How do health specialists diagnose sickle cell anaemia?

Sickles can be diagnosed by blood tests, which are haemoglobin electrophoresis and genetic testing.

6. What are the treatment options for sickle cell anaemia?

Treatments for this include pharmacological agents such as hydroxyurea, blood transfusions, and bone marrow transplantation, and modifications to lifestyle that better manage symptoms.

7. How is sickle cell anemia inherited?

Sickle cell anemia is inherited in an autosomal recessive pattern. This means a person must inherit two copies of the mutated gene (one from each parent) to develop the disease. If a person inherits only one copy, they are a carrier (sickle cell trait) but typically don't show symptoms.

8. What causes the sickle cell shape in red blood cells?

The sickle cell shape is caused by a mutation in the HBB gene, which produces hemoglobin. This mutation results in the production of abnormal hemoglobin S, which can form long chains when deoxygenated. These chains distort the red blood cell into a crescent or sickle shape.

9. What is the genetic probability of two carriers having a child with sickle cell anemia?

When both parents are carriers (have sickle cell trait), there is a 25% chance with each pregnancy of having a child with sickle cell anemia, a 50% chance of having a child with sickle cell trait, and a 25% chance of having a child with neither the disease nor the trait.

10. What is the difference between sickle cell trait and sickle cell disease?

Sickle cell trait occurs when a person inherits one copy of the sickle cell gene mutation. These individuals are carriers but usually don't have symptoms. Sickle cell disease occurs when a person inherits two copies of the mutation, resulting in the full disease with its associated symptoms and complications.

11. How does sickle cell anemia protect against malaria?

Individuals with sickle cell trait (carriers) have some protection against malaria. The parasite that causes malaria has difficulty infecting and reproducing in sickle-shaped cells. This evolutionary advantage explains why the sickle cell gene is more common in regions where malaria is prevalent.

12. What is hemoglobin S?

Hemoglobin S is the abnormal form of hemoglobin found in sickle cell anemia. It results from a single amino acid substitution in the beta-globin chain of hemoglobin. When deoxygenated, hemoglobin S can form long chains that distort the shape of red blood cells, causing them to become sickle-shaped.

13. What is the difference between sickle cell anemia and thalassemia?

While both are inherited blood disorders, sickle cell anemia results from a specific mutation causing abnormal hemoglobin S, leading to sickle-shaped cells. Thalassemia, on the other hand, is caused by mutations that reduce or prevent the production of one of the globin chains in hemoglobin, leading to reduced or absent hemoglobin production.

14. What is aplastic crisis in sickle cell anemia?

An aplastic crisis is a temporary cessation of red blood cell production in the bone marrow, often triggered by infections, particularly parvovirus B19. This can cause a rapid and severe drop in hemoglobin levels, potentially leading to life-threatening anemia if not treated promptly.

15. What is the relationship between sickle cell anemia and avascular necrosis?

Avascular necrosis, also known as osteonecrosis, is a common complication of sickle cell anemia. It occurs when sickled cells block blood flow to bones, leading to bone tissue death. This most commonly affects the hip joints but can occur in other bones as well, causing pain and potentially leading to joint collapse.

16. Are there different types of sickle cell disease?

Yes, there are several types of sickle cell disease. The most common and severe form is HbSS (sickle cell anemia). Other types include HbSC, HbS beta thalassemia, and rarer forms like HbSD, HbSE, and HbSO.

17. How is sickle cell anemia diagnosed?

Sickle cell anemia is typically diagnosed through blood tests. The most common tests are hemoglobin electrophoresis, which separates different types of hemoglobin, and genetic testing to identify the specific mutation. In many countries, newborn screening includes tests for sickle cell disease.

18. What is a hemolytic crisis in sickle cell anemia?

A hemolytic crisis occurs when there is a sudden, severe breakdown of red blood cells (hemolysis) in individuals with sickle cell anemia. This can lead to a rapid drop in hemoglobin levels, causing severe anemia, jaundice, and potentially life-threatening complications if not treated promptly.

19. What is the role of fetal hemoglobin in sickle cell anemia?

Fetal hemoglobin (HbF) doesn't form sickle shapes like adult hemoglobin S. Newborns with sickle cell genes are protected from symptoms in their first few months of life due to high levels of HbF. Some treatments, like hydroxyurea, aim to increase HbF production to reduce sickling and symptoms.

20. How does sickle cell anemia affect the cardiovascular system?

Sickle cell anemia can lead to various cardiovascular complications. These include pulmonary hypertension (high blood pressure in lung arteries), an enlarged heart due to chronic anemia, and an increased risk of stroke, especially in children. Regular cardiovascular monitoring is crucial for patients.

21. What are the main symptoms of sickle cell anemia?

The main symptoms of sickle cell anemia include pain crises (episodes of severe pain), fatigue, shortness of breath, delayed growth and puberty in children, vision problems, and an increased risk of infections. Symptoms can vary in severity and frequency among individuals.

22. How does sickle cell anemia affect the spleen?

Sickle cell anemia can severely damage the spleen, often leading to functional asplenia (loss of splenic function) or even autosplenectomy (self-destruction of the spleen). This increases the risk of severe infections, as the spleen plays a crucial role in the immune system.

23. What is a pain crisis in sickle cell anemia?

A pain crisis, also called a vaso-occlusive crisis, occurs when sickled red blood cells block small blood vessels, reducing blood flow to an area of the body. This causes sudden, severe pain that can last for hours to days and may require hospitalization for pain management.

24. How does sickle cell anemia affect oxygen transport in the body?

Sickle cell anemia impairs oxygen transport in two ways: 1) The abnormal hemoglobin S doesn't bind oxygen as effectively as normal hemoglobin. 2) The sickle-shaped cells can block small blood vessels, reducing blood flow and oxygen delivery to tissues.

25. How does altitude affect individuals with sickle cell anemia?

High altitudes can be problematic for individuals with sickle cell anemia. The lower oxygen levels at high altitudes can trigger sickling of red blood cells, potentially leading to pain crises or other complications. Patients are often advised to consult their doctor before traveling to high-altitude locations.

26. Can sickle cell anemia be cured?

Currently, the only potential cure for sickle cell anemia is a stem cell transplant (also called bone marrow transplant). However, this procedure is complex, carries significant risks, and is not suitable for all patients. Research into gene therapy as a potential cure is ongoing.

27. What are the main treatment approaches for sickle cell anemia?

Treatment for sickle cell anemia focuses on managing symptoms and preventing complications. This includes pain management, blood transfusions, hydroxyurea medication to increase fetal hemoglobin production, and preventive measures like vaccinations and antibiotics to reduce infection risk.

28. How does hydroxyurea help in treating sickle cell anemia?

Hydroxyurea helps by stimulating the production of fetal hemoglobin (HbF), which doesn't sickle like adult hemoglobin S. Increased HbF reduces the formation of sickle cells, decreasing pain crises and other complications. It also reduces the need for blood transfusions in many patients.

29. What is the life expectancy for individuals with sickle cell anemia?

With modern treatments, the life expectancy for individuals with sickle cell anemia has improved significantly. Many patients now live into their 40s, 50s, and beyond. However, life expectancy can vary based on the severity of the disease, access to healthcare, and individual factors.

30. How does sickle cell anemia affect pregnancy?

Sickle cell anemia can complicate pregnancy, increasing risks for both mother and baby. Pregnant women with sickle cell anemia have a higher risk of pain crises, infections, and pregnancy-related complications. The baby may be at risk for growth restriction and preterm birth. Close medical monitoring is essential.

31. How does sickle cell anemia affect growth and development in children?

Sickle cell anemia can delay growth and puberty in children. The chronic anemia and increased energy demands of the body can lead to slower growth rates. Additionally, the disease can affect bone development and potentially cause cognitive challenges due to silent strokes or chronic oxygen deprivation.

32. What is priapism and how is it related to sickle cell anemia?

Priapism is a painful, prolonged erection not related to sexual arousal. It's a potential complication of sickle cell anemia, occurring when sickled cells block blood flow in the penis. If not treated promptly, priapism can lead to permanent erectile dysfunction.

33. How does sickle cell anemia affect the kidneys?

Sickle cell anemia can damage the kidneys in several ways. The abnormal blood flow can lead to reduced kidney function, problems concentrating urine, and an increased risk of kidney infections. Over time, some patients may develop chronic kidney disease or kidney failure.

34. What is the relationship between sickle cell anemia and stroke?

Individuals with sickle cell anemia, especially children, have an increased risk of stroke. This is due to sickled cells blocking blood flow in brain arteries. Regular screening with transcranial Doppler ultrasound and preventive measures like blood transfusions can help reduce this risk.

35. How does sickle cell anemia affect the eyes?

Sickle cell anemia can lead to various eye problems, including retinopathy (damage to the retina), which can cause vision loss. The abnormal blood flow can also affect other parts of the eye, potentially leading to complications like glaucoma or retinal detachment.

36. How does sickle cell anemia affect the lungs?

Sickle cell anemia can lead to various lung complications, including acute chest syndrome (a life-threatening condition involving chest pain, fever, and lung infiltrates), pulmonary hypertension, and an increased susceptibility to respiratory infections.

37. How does sickle cell anemia affect bone health?

Sickle cell anemia can significantly impact bone health. The chronic anemia and reduced blood flow can lead to bone infarction (death of bone tissue), osteonecrosis (particularly in the hip and shoulder joints), and an increased risk of osteoporosis. These issues can cause chronic pain and mobility problems.

38. What is the role of blood transfusions in managing sickle cell anemia?

Blood transfusions play a crucial role in managing sickle cell anemia. They can be used to treat severe anemia, prevent stroke in high-risk patients, manage acute complications like acute chest syndrome, and prepare patients for surgery. Regular transfusions can also help reduce the frequency of pain crises.

39. How does sickle cell anemia affect the liver?

Sickle cell anemia can cause various liver complications. These include hepatic sequestration (trapping of sickled cells in the liver), leading to sudden liver enlargement and anemia, chronic liver disease due to iron overload from frequent transfusions, and an increased risk of gallstones due to excessive breakdown of red blood cells.

40. What is the concept of genetic counseling in sickle cell anemia?

Genetic counseling for sickle cell anemia involves educating individuals and couples about the inheritance pattern of the disease, the risk of having affected children, and available testing options. It helps people make informed decisions about family planning and understand the implications of carrier status or disease diagnosis.

41. How does sickle cell anemia affect the immune system?

Sickle cell anemia can compromise the immune system in several ways. The damaged spleen reduces the body's ability to fight certain infections. Additionally, the chronic inflammation associated with the disease can alter immune function. This leads to an increased susceptibility to infections, particularly from encapsulated bacteria.

42. What is hemoglobin electrophoresis and how is it used in diagnosing sickle cell anemia?

Hemoglobin electrophoresis is a laboratory test that separates different types of hemoglobin based on their electrical charge. In diagnosing sickle cell anemia, it can identify the presence of hemoglobin S and quantify the amounts of different hemoglobin types. This test is crucial for confirming the diagnosis and differentiating between sickle cell trait and disease.

43. How does sickle cell anemia affect wound healing?

Sickle cell anemia can impair wound healing due to reduced blood flow and oxygen delivery to tissues. The chronic anemia and potential for vaso-occlusion in small blood vessels can slow the healing process, increasing the risk of chronic wounds or ulcers, particularly in the legs.

44. How does sickle cell anemia affect male fertility?

Sickle cell anemia can impact male fertility in several ways. The chronic anemia and potential for vaso-occlusion can affect testicular function. Additionally, complications like priapism can lead to erectile dysfunction. Some men with sickle cell anemia may have reduced sperm count or quality.

45. What is the role of nitric oxide in sickle cell anemia?

Nitric oxide plays a crucial role in maintaining normal blood flow by relaxing blood vessels. In sickle cell anemia, the breakdown of abnormal red blood cells releases free hemoglobin, which scavenges nitric oxide. This reduction in nitric oxide can contribute to vaso-occlusion and various complications of the disease.

46. How does sickle cell anemia affect pain perception?

Chronic pain is a hallmark of sickle cell anemia, and over time, it can alter pain perception. Some patients may develop heightened sensitivity to pain (hyperalgesia) or pain from stimuli that wouldn't normally cause pain (allodynia). This can complicate pain management and affect quality of life.

47. What is the concept of cerebral vasculopathy in sickle cell anemia?

Cerebral vasculopathy in sickle cell anemia refers to the damage and narrowing of blood vessels in the brain. This can lead to reduced blood flow, increasing the risk of stroke and cognitive impairment. Regular screening with transcranial Doppler ultrasound is recommended to assess this risk, especially in children.

48. How does sickle cell anemia affect the endocrine system?

Sickle cell anemia can impact various endocrine glands. It can lead to growth hormone deficiency, affecting growth in children. Thyroid and adrenal gland function may also be affected. In addition, damage to the pituitary gland can cause various hormonal imbalances, potentially affecting puberty, fertility, and metabolism.

49. What is the concept of silent cerebral infarcts in sickle cell anemia?

Silent cerebral infarcts are small strokes that occur without obvious symptoms in individuals with sickle cell anemia. Despite being "silent," they can lead to cognitive impairment over time. Regular MRI screening is often recommended to detect these infarcts, especially in children, to guide preventive measures.

50. How does sickle cell anemia affect exercise tolerance?

Sickle cell anemia can significantly reduce exercise tolerance due to chronic anemia, which limits oxygen delivery to tissues. Additionally, intense exercise can potentially trigger sickling and pain crises. However, moderate, regular exercise is often encouraged as part of overall health management, under medical supervision.

51. What is the role of L-glutamine in treating sickle cell anemia?

L-glutamine is an amino acid that has been approved as a treatment for sickle cell anemia. It works by reducing oxidative stress in red blood cells, which can help prevent sickling. L-glutamine has been shown to reduce the frequency of pain crises and hospitalizations in some patients.

52. How does sickle cell anemia affect sleep?

Sickle cell anemia can significantly impact sleep quality. Chronic pain