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

What is 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.

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 type of 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 the prognosis was very poor. The medical science has generally provided a 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.

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. It can be done by blood tests and genetic testing as well. 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 anaemia, 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 the HBB gene mutation.

Treatment of Sickle Cell Anaemia

Sickle cell anaemia is managed by a comprehensive approach 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 when compatible donors are available.

Lifestyle and Home Remedies

The patients are warned about observing fluid intake, good nutrient intake, 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.

MCQs on Sickle Cell Anaemia

Q1. A person with sickle cell anaemia is

Option 1: more prone to malaria

Option 2: more prone to typhoid

Option 3: less prone to malaria

Option 4: less prone to typhoid

Correct answer: (3) less prone to malaria.

Explanation:

Patients suffering from sickle cell anaemia demonstrate a distinct kind of immunity against malaria due to the abnormally shaped RBCs. Since the parasite will find less favour in sickle-shaped RBCs, severe infection would occur less often. This protection is confirmed through multiple clinical research works, mainly from malaria-prone areas where this sickle cell trait has occurred as an intrinsic mechanism for defending against malaria.

Hence, the correct answer is Option (3) less prone to malaria.

Q2. Select the correct match

Option 1: Haemophilia-Y linked

Option 2: Phenylketonuria- Autosomal dominant trait

Option 3: Sickle cell anaemia- Autosomal recessive trait chromosome 11

Option 4: Thalassemia- X linked

Correct answer: (3) Sickle cell anaemia- Autosomal recessive trait chromosome 11.

Explanation:

Sickle cell anemia is an autosomal recessive genetic disorder located on chromosome 11, caused by a mutation in the gene encoding hemoglobin. This mutation leads to the production of abnormal hemoglobin, known as hemoglobin S, which causes red blood cells to adopt a sickle shape. These abnormally shaped cells are less flexible and can get stuck in small blood vessels, disrupting blood flow and leading to symptoms like anemia, pain crises, and other serious health complications. Individuals must inherit two copies of the sickle cell gene (one from each parent) to express the disease.

Hence, the correct answer is option (3) Sickle cell anaemia- Autosomal recessive trait chromosome 11.

Q3. Which of the following statements is the most appropriate for sickle cell anaemia?

Option 1: It cannot be treated with iron supplements

Option 2: It is a molecular disease

Option 3: It confers resistance to acquiring malaria

Option 4: All of the above

Correct answer: 4) All of the above

Explanation:

Sickle cell anaemia is a genetic disorder caused by a mutation in the haemoglobin gene, leading to the production of abnormal haemoglobin. Iron supplements cannot be used to treat it because the disorder is related to the shape and function of red blood cells, not iron deficiency. The altered, sickle-shaped red blood cells can block blood flow and cause pain, but they also provide resistance to malaria. The malaria parasite, Plasmodium, is less able to survive in sickle-shaped cells, offering a protective advantage in malaria-endemic regions. However, sickle cell anaemia still leads to various health complications, requiring supportive treatment and management.

Hence, the correct answer is option 4) All of the above

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