SICKLE CELL DISEASE

Sickle Cell Disease

Sickle Cell Disease is a group of hereditary blood disordrs affecting Red Blood Cells, with high morbidity and death rates. There are different types of sickle cell disease including sickle cell hemoglobin C (SC) disease, sickle cell hemoglobin D (SD) disease, and sickle cell beta-thalassemia which are less severe forms of sickle cell disease. Sickle cell anemia is a more severe form. According to World Health Organization, it is the most prevalent genetic disease in the WHO African Region. In many countries, 10%–40% of the population carries the sickle-cell gene resulting in estimated SCD prevalence of at least 2%.

Normal Red Blood Cells are biconcave discs and are pliable or flexible which enables them deform without rupturing and squeeze through narrow blood capillaries. Red Blood Cells live up to about one hundred and twenty (120) days after which they are destroyed by macrophages in the spleen, liver or red bone marrow and their components recycled to make new Red Blood Cells. Mature Red Blood Cells consist primarily of hemoglobin proteins, which help Red Blood Cells transport oxygen from the lungs to the tissues of the body by bonding to oxygen molecules.

Normal Red Blood Cells vs. Sickled Red Blood Cells

In sickle cell disease however, after releasing oxygen to tissues, the mutated hemoglobins lock together into rigid rows. Rods of hemoglobin cause Red Blood Cells to deform into long pointed sickle shape. Sickled Red Blood Cells lose their elasticity, become deformed, rigid and sticky. As a result, these sickled Red Blood Cells adhere to the inner lining of blood vessels and pile up one on another, reducing blood flow to a region or an organ. Sickled Red Blood Cells may also completely occlude small blood vessels. The sickling process takes time, if the Red Blood Cell is exposed to enough oxygen (for example if the Red Blood Cell goes through pulmonary circulation) again before its membrane becomes too rigid, it will return to its normal biconcave shape which is pliable. This is why the “sickling crises” are intermittent. Narrowing or occlusion of a blood vessel prevents oxygen from reaching a wide range of cells causing the various symptoms people with sickle cell disease experience.

Signs and Symptoms of Sickle Cell Disease

Most newborns with sickle cell disease do not experience any symptoms till they are about 5 or 6 months old before they begin to experience episodes of excruciating pain at oxygen starved areas of the body. The general signs and symptoms experienced by persons with sickle cell disease include; stunted growth and short stature, frontal bossing and gnatopathy, jaundice and pallor.

The cause of stunted growth and short stature in people with sickle cell disease is not well understood. However, children with sickle cell disease do not grow well, they grow slowly even reaching puberty later than their peers and this may be because they are always sick and they do not get enough oxygen delivered to their tissues as a result of fewer healthy red blood cells. One of the functions of zinc in the body is cell growth but in sickle cell disease, there is excessive excretion of zinc in urine as a result of anemia leading to zinc deficiency which may contribute to stunted growth in children with sickle cell disease. Most adults with sickle cell disease are also shorter and thinner than the general population.

Sickle cell patients may experience frontal bossing which is a prominent protuberance of the forehead and gnatopathy which refers to jaw protrusion. This happens because, in the normal body, red blood cells are normally produced by long bones but in sickle cell disease, the rate at which red blood cells are destroyed is high due to their short lifespan (60-90 days). As a result, these long bones are unable to keep up with red blood cell production so the body compensates for this by employing other bones such as those of the jaw and frontal bone of the skull to also produce red blood cells causing these bones to enlarge. Extramedullary hematopoiesis, that is, red blood cell production outside the bone marrow can also happen, most often in the liver causing hepatomegaly (liver enlargement).

Frontal bossing in a child - frontal bossing is the protrusion of the frontal bones.

Sickled red blood cells do not live as long as normal red blood cells and so there is rapid destruction of red blood cells than the liver can deal with. Bilirubin (which causes yellow appearance on the sclera and the skin) is released from these broken down cells and build up in the body resulting in a condition called Jaundice.

Anemia refers to a condition where there is insufficient healthy red blood cells to carry oxygen to various tissues of the body. This occurs a lot in people with sickle cell disease because their red blood cells are unhealthy and have short lifespan. This can lead to pale appearance of the skin known as pallor.

Sickle Cell Crises

There are about four types of sickle cell crises including vaso-occlusive crisis, aplastic crisis, splenic sequestration crisis, acute chest syndrome, and hemolytic crisis which may be triggered by infections, acidosis, high altitude, stress, extremes of temperature, malaria, strenuous exercise, and dehydration. Each episode may last for about 5-7 days.

Vaso-occlusive crisis occurs when sickled red blood cells obstruct capillaries and restrict blood flow to surrounding organs. Vaso- occlusion can occur in any organ of the body. Starting from infancy, sickled red blood cells can occlude blood vessels in the feet and hands causing dactylitis (inflammation of the digits). Vaso- occlusion in the spleen can lead to splenic infarct or death which over time can lead to auto splenectomy, which scars down and finally disappears from the body. The spleen is mostly affected because of its narrow blood vessels and function of clearing defective or worn out red blood cells. Nonfunctional or absence of a spleen makes the body susceptible to infections because macrophages in the spleen destroy encapsulated bacteria by opsonizing and engulfing them. Prophylactic or preventive antibiotics are given to protect people with sickle cell disease from bacterial infection. Sickled red blood cells may also clog up in blood vessels of the brain , which may lead to stroke. Occlusion of blood vessels in the renal papillae can lead to necrosis, manifesting as hematuria (blood in urine) and proteinuria (proteins in urine). A blockage in the eye may cause vision problems. In men, occlusion of blood vessels in the penis can lead to priapism (unaroused,painful and prolonged erection).

Sickled or crescent red blood cells blocking a blood vessel. This reduces blood flow to the surrounding tissues leading to pain, ischaemia and death of the tissues.

Vaso- occlusive crisis that occurs in the lungs is known acute chest syndrome and it presents with symptoms of cough, difficulty breathing, chest pain, fever, or hypoxaemia. It is the second most common complication of sickle cell disease and accounts for about 25% of deaths in patients with sickle cell disease.

Splenic sequestration crisis is the acute, painful enlargement of the spleen which occurs as a result intrasplenic trapping of red blood cells. This leads to a drastic fall in the haemoglobin levels with the risk of hypovolemic shock (a condition in which severe blood or fluid loss makes the heart unable to pump enough blood to the rest of the body). It is considered an emergency because the patient may die within 1-2 hours if not treated, due to circulatory failure.

Haemolytic crisis is an acute increased fall in haemoglobin level. This is because sickled red blood cells have short lifespans and are broken down faster. Haemolytic crisis is mostly common in people with G6PD deficiency.

In aplastic crisis, erythrovirus B19 (parvovirus B19) directly affects red blood cell production by invading and multiplying in progenitor cells (cells that differentiate into other cells including reticulocytes) and destroying them. The parvovirus completely stops red blood cell production for two to three days. In the normal body, this may not cause any harm but in sickle cell disease where red blood cells have very short lifespan, it is a catastrophe.

Sickle Cell Trait

Sickle Cell Disease occurs when one inherit two sickle cell genes, one from each parent but some people inherit one sickle cell gene and one normal gene and this is called sickle cell trait. People with sickle cell trait usually do not have any of the symptoms of sickle cell disease, but can pass the trait on to their children.

How is Sickle Cell Disease Diagnosed?

🎀 Chorionic villus sampling and Amniocentesis can be done in unborn children to test for sickle cell disease or trait.

🎀 High performance liquid chromatography can also be done in early infancy to detect the presence of HbS.

🎀 In adults, sickling test and haemoglobin electrophoresis can be done.

Treatment of Sickle Cell Disease

🎀 Hydroxyurea helps to reduce the rates of painful episodes, acute chest syndrome, need for transfusions and hospitalization and prolongs life.

🎀 Hematopoietic stem cell transplant is the only cure for sickle cell disease and it is done for children less than 16 years old but it is a very expensive procedure. It is also very difficult to find a bone marrow donor who is a perfect match, unless one has an identical twin.

🎀 Blood transfusion can be done to reduce the risks of some complications of sickle cell disease such as aplastic crisis as well as severe anaemia. It may also help in the prevention of first stroke in children with sickle cell disease.

🎀 Supportive Care includes pain management with opioids (e.g. morphine) and NSAIDS (e.g. diclofenac), infection prevention with antibiotics and fluid therapy to prevent dehydration.

How to Reduce the Occurrence of Sickle Cell Disease

🎀 Drink plenty of water to prevent dehydration.

🎀 Try to avoid getting too hot or too cold.

🎀 Try to avoid places or situations that expose you to low oxygen levels like climbing a mountain or strenuous exercise.

🎀 Try to reduce or avoid stress in your life.

Genetic counselling and testing is very important especially in making marriage and pregnancy decisions because it helps people to understand how genetic succession contribute to the occurrence or risk of genetic diseases such as Sickle Cell Disease, thereby relatively decreasing the prevalence of the disease.

Ms_Seidu💕

Picture source: Google

Read more👇

https://www.nhs.uk

https://www.cdc.gov

https://apps.who.int