What is sickle cell anaemia?

Sickle cell anaemia (sickle cell disease) is a disorder of the blood caused by an inherited abnormal haemoglobin (an oxygen-carrying protein within the red blood cells). The abnormal haemoglobin causes distorted (sickled) red blood cells. The sickled red blood cells are fragile and prone to rupture. When the number of red blood cells decreases from ruptured (haemolysis), anaemia is the result. This condition is referred to as sickle cell anaemia. The irregular sickled cells can also block blood vessels causing tissue and organ damage and pain.

Sickle cell anaemia is one of the most commonly inherited blood anaemia’s. The disease primarily affects Africans and African Americans.

How is sickle cell anaemia inherited?

Sickle cell anaemia is inherited as an autosomal recessive condition (meaning that the gene is not linked to a sex chromosome) whereas sickle cell trait is inherited as an autosomal dominant trait. This means that the gene can be passed on from a parent In order for sickle cell anaemia to occur, a sickle cell gene must be inherited from both the mother and the father, so that the child has two sickle cell genes.

The inheritance of just one sickle gene is called sickle cell trait or the "carrier" state. Sickle cell trait does not cause sickle cell anaemia. Persons with sickle cell trait usually do not have many symptoms of disease and have normal hospitalization rates and life expectancies.

Sickle cell trait is present in some two million blacks in the United States (8% of the U.S. black population at birth). When two carriers of sickle cell trait conceive, their offspring have a one in four chance of having sickle cell anaemia. (In some parts of Africa, one in five people carry sickle cell trait.)

What conditions promote the sickling of the red blood cells?

The sickling is promoted by conditions which are associated with low oxygen levels, increased acidity, or low volume (dehydration) of the blood. These conditions can occur as a result of injury to the body's tissues, dehydrating states, or anaesthesia. Even certain organs are predisposed to lower oxygen levels or acidity, such as when blood moves slowly through the spleen, liver, or kidney. Also, organs with particularly high metabolic rates (such as the brain, muscles, and the placenta in a pregnant woman) promote sickling by extracting more oxygen from the blood. These conditions make these organs susceptible to injury from sickle cell anaemia.

What are the symptoms and treatments of sickle cell anaemia?

Virtually all of the major symptoms of sickle cell anaemia are the direct result of the abnormally shaped, sickled red blood cells blocking the flow of blood that circulates through the tissues of the body. The tissues with impaired circulation suffer damage from lack of oxygen. Damage to tissues and organs of the body can cause severe disability Sickle Cell Disease in patients with sickle cell anaemia. The patients endure episodes of intermittent "crises" of variable frequency and severity, depending on the degree of organ involvement.

The major features of sickle cell anaemia include:

• Fatigue and Anaemia
• Pain Crises Dactylitis (swelling and inflammation of the hands and/or feet) and Arthritis
• Bacterial Infections
• Splenic Sequestration (sudden pooling of blood in the spleen) and Liver Congestion
• Lung and Heart Injury
• Leg Ulcers
• Aseptic Necrosis and Bone Infarcts (death of portions of bone)
• Eye Damage
• Other Features

Whilst some symptoms are age secific, many typically occur in certain age groups. Sickle cell anaemia usually first presents symptoms in the first year of life. Infants and younger children can suffer with fever, abdominal pain, pneumococcal bacterial infections, painful swellings of the hands and feet (dactylitis), and splenic sequestration. Adolescents and young adults more commonly develop leg ulcers, aseptic necrosis, and eye damage. Symptoms in adults are typically intermittent episodes due to injury of bone, muscle, or internal organs.

Affected infants do not develop symptoms in the first few months of life because the hemoglobin produced by the developing fetus protects the red blood cells from sickling. This fetal hemoglobin is absent in the red blood cells that are produced after birth so that by 5 months of age, the sickling of the red blood cells is prominent and symptoms begin.

Generally, treatment is directed at the management and prevention of acute manifestations. Therapies are directed toward blocking the red blood cells from stacking together. There is no single remedy to reverse the anaemia. It is, therefore, important that family members have an optimal understanding of the illness and communication with the doctors and medical personnel be maintained.

Fatigue and Anaemia

Fatigue is another common symptom. The sickled red blood cells are prone to breakageshortening their life span. Typically, the site of red blood cell production (bone marrow) works overtime to produce these cells rapidly, attempting to compensate for their destruction in the circulation. Occasionally, the bone marrow suddenly stops producing the red blood cells which causes a very severe form of anaemia (aplastic crises). Aplastic crises can be promoted by infections that otherwise would seem less significant, including viruses of the stomach and bowels and the flu.

Pain Crises

Pain crises are the result of inadequate blood supply to body tissues. The impaired circulation is caused by the blockage of various blood vessels from the sickling of red blood cells. The sickled red blood cells slow or impede the normal flow of blood through the tissues. This leads to excruciating pain requiring hospitalization and narcotic medication for relief. The pain typically is throbbing and can change its location from one body area to another. Bone is frequently affected. Pain in the abdomen with tenderness is common and can mimic appendicitis. Fever frequently is associated with the pain crises.

A pain crisis can be caused by dehydration, infection, injury, cold exposure, emotional stress, or strenuous exercise. As a prevention measure, persons with sickle cell should avoid extremes of heat and cold. Pain crises require medications for pain and increased fluid intake. Dehydration must be prevented to avoid further injury to the tissues and intravenous fluids can be necessary. Along with the fluids clotrimazole and magnesium are often given.

For further details please visit:
www.sicklecellsociety.org