Sickle Cell

Sickle cell is a term used to describe any condition that involves inherited sickle-cell hemoglobin of the blood. There are many different causes of human disease: malnutrition, infection, radiation, physical injury, and mistakes in body chemistry. Sickle cell disease is the result of the last one. It cannot be outgrown, and those who are not born with it cannot contract it. It is not contagious and not caused by anything with which a person might come in contact. Painful episodes are characteristic. Other problems also include the vulnerability to infection, anemia, organ damage, and a tendency to form gallstones. Understandably, emotional problems can be expected to follow the physical ones.

Normal hemoglobin, called hemoglobin A or hemoglobin C, is characterized by round red blood cells which flow easily through the body's vessels. Sickle-cell hemoglobin, called hemoglobin S (HbS) is contained in sickle-shaped, elongated cells that resist flow and cause obstructions in circulation (microinfarctions), a lack of oxygen to the tissues (hypoxia), and the proliferation of additional sickle cells. Sickle cells also have a shorter than average lifetime -– 20 days as opposed to 120 of normal red blood cells. Sickle-cell disease occurs when hemoglobin A is changed to hemoglobin S by a genetic substitution of one amino acid in the hemoglobin chain.

When sickle cell hemoglobin cannot reach other parts of the body, a series of problems develop, often referred to as a “crisis”. Hemoglobin travels inside a red blood cell which must squeeze through tiny blood vessels, as well as the larger ones. Normally, squeezing through tiny capillaries poses no problem because the disc-shaped cell is always soft and flexible. However, inside a sickled red blood cell, crystals form that twist the cell out of shape, causing it to lose softness and flexibility, which damages the cell membrane itself.

This type of damage has the following effects. Since the red blood cells cannot squeeze through small blood vessels, the vessels become clogged and blood flow backs up so that oxygen cannot be delivered to organs and tissues. When an organ has its oxygen supply cut off, damage begins, causing pain and other problems. The damage can be serious and the pain excruciating. When red blood cells are damaged, the body destroys them, but so many are damaged and destroyed in sickle cell crisis that the patient suffers from chronic anemia. Therefore, such people are more susceptible to infections and are frequently incapacitated.

Sickle cell disease is most common among those of African descent and those with ancestors from Puerto Rico, Cuba, Haiti, Jamaica, Italy, Sicily, Greece, Cyprus, Turkey, Syria, and South India. It affects about one in 375 Americans of African descent, and the trait is present in one out of every ten. Some of these individuals know they carry the gene. Others do not.

However, many people do not realize that whites can also carry the sickle cell gene. A blonde-haired, blue-eyed person can have sickle cell disease, which occurs mainly among whites from the Middle East, India, and the Mediterranean. It is also common among Israeli Arabs, Saudis, and Turks. The case that led to the important discovery by Dr. William Castle in 1938 that sickling slows down the blood flow, involved a white woman from Cleveland, Ohio, whose family was Italian.

Various forms of sickle cell are often used interchangeable, but the correct terms are as follows:

Acquiring sickle cell
The following six scenarios will show the probablility of acquiring the sickle cell gene.

  1. Both parents have sickle cell disease. Since sickle cell disease is recessive, both parents must have two copies of the HbS gene or they would not have the disease. Therefore, no matter which gametes combine to form a child, the results will be the same; and every child of this union will receive one HbS gene from its mother and one from its father. All children born to this couple will have sickle cell disease.

  2. One parent has sickle cell disease and the other has the sickle cell trait. The parent with the disease has only the HbS genes. Therefore, all of his/her gametes will have HbS genes. The other parent has one HbS gene and one HbA gene. Therefore, the odds of that parent transmitting either gene are 50/50. For this couple, two types of conception are equally possible -- one between two gametes carrying HbS genes, and one between a gamete carrying an HbS gene and a gamete carrying an HbA gene. All children born to this couple will display either sickle cell disease or sickle cell trait. The odds are 50/50 for each.

  3. One parent has sickle cell disease and the other parent is normal. In this case, "normal" means that both of the hemoglobin genes are HbA. All gametes of the sickle cell parent will carry the HbS gene and all the gametes of the normal parent will carry the HbA gene. Therefore, all their children will inherit one normal and one sickle cell gene and all the children will have the sickle cell trait.

  4. Both parents have the sickle cell trait. Both parents have an equal chance of transmitting either gene. Half of the time, one parent will transmit the HbS gene which will have an equal chance of combining with another HbS gene or with an HbA gene from the other parent. The other half of the time, the first parent will transmit an HbA gene which will also have an equal chance of combining with an HbS gene or an HbA gene from the other parent. This all means that there is a 25% chance that there will be a union of an HbS gene with another HbS gene, a 50% chance that there will be a union of an HbS gene with an HbA gene, and a 25% chance of a union between an HbA gene and another HbA gene. Therefore, children born to this couple will have a 25% chance of contracting sickle cell disease, a 50% chance of carrying sickle cell trait, and a 25% chance of being normal.

  5. One parent has sickle cell trait and the other is normal. Half of the gametes of the parent with the sickle cell trait will carry the HbS gene and half will carry the HbA gene. Since all the gametes of the other normal parent will carry an HbA gene, half of the conceptions will result in a union of an HbS gene with an HbA gene and half will result in a union of two HbA genes. All the children of this couple will either display sickle cell trait or be normal -- the chances are 50/50 for each.

  6. Both parents are normal. Neither parent has a sickle cell gene to transmit. All children born to this couple will be normal. This will be the case even if the preceding generation (the parents) carried sickle cell genes.

Lifetime outline
The following is an outline of a lifetime and what can be expected by a sickle cell patient. However, not all are alike and will not display every complication of the disease. In addition, some complications are common while others are rare, occurring only in acute episodes.

Crisis
Sickle cell disease is painful. Not always, and not necessarily often, but painful episodes are characteristic of the disease and are often referred to as "crisis" periods. These may last a few days or sometimes for weeks and are often preceded by an infection, cold, or sore throat. Crisis may recur several times a year with the patient remaining quite healthy between occurrences. Crisis periods may range in intensity from annoying to excruciating.

Most of the painful episodes occur when abnormal blood cells block small blood vessels. When these vessels are blocked, blood cannot flow through them and deliver oxygen to the parts of the body supplied by these vessels. When the body parts are deprived of oxygen, they release chemicals that cause pain; and, if the blood flow is not restored, tissue damage follows. Where tissue is damaged, the area becomes inflamed; and this, too, becomes a source of pain. Fever often accompanies painful episodes.

There are several types of sickle cell crisis which can occur, including vaso-occlusives (VOCs), acute splenic squestration, aplastic, hyperhemolytic, stroke, chest syndrome, and infection. These crises may occur individually or with one or more of the other crisis.

It is difficult to predict what will trigger a painful episode, but some indications point to infections, too little fluid intake, cold weather, excessive physical stress, and emotional pain. The parts of the body in which painful episodes are most common are the bones, chest, and abdomen.

Any and all organs can be damaged by sickle cell disease and most of it is caused by blocked blood vessels, a characteristic of sickle cell disease. The following areas are examples of such damage that can occur:

Psychological Damage
Another aspect of sickle cell disease that few address involves the psychological effects. Any chronic disease will have an emotional impact both on the individual and the family. Since the disease begins from birth, it is the children who suffer the most. By the time adulthood is reached, compensatory techniques have usually been adopted.

During hospital stays, sickle cell children must be separated from their families, causing some to fear abandonment. Severe pain, isolation, and disability take their toll on them and their families. Anxiety is common and for some, the fear of death. Sickle cell children are often smaller and thinner than their healthy peers. They look different and may find themselves less intellectually competent since many lose time from school as a result of crisis episodes. Low self esteem is common in children and adolescents, who may become socially withdrawn. Some suffer from depression, which seems to be associated with episodes of pain. Consequently, they become dependent on, and sometimes addicted to, drugs.

All sickle cell patients, regardless of age, need sound emotional support.