What is sickle cell anemia disease?

Sickle cell disease is an inherited blood disorder that affects red blood cells. People with sickle cell disease have red blood cells that contain mostly hemoglobin, an abnormal type of hemoglobin. Sometimes these red blood cells become sickle-shaped (crescent shaped) and have difficulty passing through small blood vessels.

When sickle-shaped cells block small blood vessels, less blood can reach that part of the body. Tissue that does not receive a normal blood flow eventually becomes damaged. This is what causes the complications of sickle cell disease. There is currently no universal cure for sickle cell disease.

Hemoglobin – is the main substance of the red blood cell. It helps red blood cells carry oxygen from the air in our lungs to all parts of the body. Normal red blood cells contain hemoglobin A. Hemoglobin S and hemoglobin C are abnormal types of hemoglobin. Normal red blood cells are soft and round and can squeeze through tiny blood tubes (vessels). Normally, red blood cells live for about 120 days before new ones replace them.

People with sickle cell conditions make a different form of hemoglobin A called hemoglobin S (S stands for sickle). Red blood cells containing mostly hemoglobin S do not live as long as normal red blood cells (normally about 16 days). They also become stiff, distorted in shape and have difficulty passing through the body’s small blood vessels. When sickle-shaped cells block small blood vessels, less blood can reach that part of the body. Tissue that does not receive a normal blood flow eventually becomes damaged. This is what causes the complications of sickle cell anemia.

What Causes Sickle Cell Disease?

Sickle cell disease is caused by a genetic abnormality in the gene for hemoglobin, which results in the production of sickle hemoglobin. When oxygen is released from sickle hemoglobin, it sticks together and forms long rods, which damage and change the shape of the red blood cell. The sickle red blood cells causes the symptoms of sickle cell disease.

Children are born with sickle cell disease; it is not contagious. It occurs when a child inherits two sickle hemoglobin genes, one from each parent. About 2,000 babies are born with sickle cell disease each year in the United States. People who inherit only one sickle hemoglobin gene are carriers (sickle cell trait) and do not have anemia or painful sickle cell crises. About 2 million Americans have sickle cell trait.

What is sickle cell anemia inherited?  

Sickle cell anemia is inherited as an autosomal (meaning that the gene is not linked to a sex chromosome) recessive condition whereas sickle cell trait is inherited as an autosomal dominant trait. This means that the gene can be passed on from a parent carrying it to male and female children. In order for sickle cell anemia 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 anemia. 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 mate, their offspring have a one in four chance of having sickle cell anemia. (In some parts of Africa, one in five persons is a carrier for sickle cell trait.)

What is a sickle trait?

The treatment of sickle cell anemia is designed according to which of the individual features of the illness are present. In general treatment is directed at the management and prevention of the acute manifestations as well as therapies directed toward blocking the red blood cells from stacking together. There is no single remedy to reverse the anemia. It is, therefore, important that family members have an optimal understanding of the illness and that communication with the doctors and medical personnel be maintained.

Fatigue and Anemia 

 Fatigue is a common symptom in persons with sickle cell anemia. Sickle cell anemia causes a chronic form of anemia which can lead to fatigue. The sickled red blood cells are prone to breakage (rupture) which causes a much shorter life span of these cells (the normal life span of a red blood cell is 120 days). These sickled red blood cells are easily detected with a microscope examination of a smear of blood on a glass slide.

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 anemia (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 (influenza).

The anemia of sickle cell anemia tends to stabilize without specific treatments. The degree of anemia is defined by measurement of the blood hemoglobin level. Hemoglobin is the protein molecule in red blood cells which carries oxygen from the lungs to the body's tissues and returns carbon dioxide from the tissues to the lungs. Blood hemoglobin levels in persons with sickle cell anemia are generally between 6 to 8 gms/dl (normal levels are above 11 gms/dl). Occasionally, there can be a severe drop in hemoglobin requiring a blood transfusion to correct the anemia (such as in patients suffering splenic sequestration). Blood transfusion is usually reserved for those patients with other complications, including pneumonia, lung infarction, stroke, severe leg ulceration, or late pregnancy. (Among the risks of blood transfusion are hepatitis, infection, immune reaction, and injury to body tissues from iron overload.) Transfusions are also given to patients to prepare them for surgical procedures. Folic acid is given as a supplement.

If sickle cell trait is not an illness, why are people test?

Sickle Cell Test

A sickle cell test is a blood test done to screen for sickle cell trait or sickle cell disease. Sickle cell disease is an inherited blood disease that causes red blood cells to be deformed. The red blood cells deform because they contain an abnormal type of hemoglobin, called hemoglobin S, instead of the normal hemoglobin, called hemoglobin A.

Sickled blood cells are destroyed by the body faster than normal blood cells. This causes anemia. Also, sickled cells can get trapped in blood vessels and reduce or block blood flow. This can damage organs, muscles, and bones and may lead to life-threatening conditions.

The best way to screen for sickle cell trait or sickle cell disease is to examine the blood using a method called high-performance liquid chromatography (HPLC). This test identifies which type of hemoglobin is present. To confirm the results of HPLC, a genetic test may be done.

Sickle cell disease is an autosomal recessive disease. This means that to have the disease, a person must inherit a gene for the disease from both parents. Each person inherits two genes (one from each parent). As a result, a person may have:

Two genes that make normal hemoglobin (hemoglobin A). These people have normal red blood cells, unless they have some other disease.

One gene that makes hemoglobin A and one that makes hemoglobin S. These people carry the sickle cell trait (and are called "a carrier"), but they do not have sickle cell disease. Sickle cell trait is usually a harmless condition.

Two genes that make hemoglobin S. These people have sickle cell disease. Both parents either carry the sickle cell trait or have the disease. Sickled red blood cells often cause recurring health problems called sickle cell crises.

One gene that makes hemoglobin S and one that makes some other abnormal type of hemoglobin. Depending on the other type of abnormal hemoglobin, these people may have mild or severe sickle cell disorder.

In conclusion A sickle cell test screens for sickle cell trait or sickle cell disease in people at high risk. Detecting sickle cell trait is important for couples who want to have children and who may be carriers of sickle cell trait.

What medical problems are caused by sickle cell disease?

The effects of sickle cell disease vary greatly from one person to the next. Some affected individuals are generally healthy, while others are frequently hospitalized. Common problems seen in sickle cell disease include the following:

  

Anemia: Individuals with sickle cell disease have a decreased number of red blood cells. As a result, they may be pale, tire easily and have shortness of breath.

Infections: Infants and young children with sickle cell disease have an increased risk of contracting serious bacterial infections, such as pneumonia and meningitis (infection of the lining of the brain). Infections are a major cause of death in children with sickle cell disease.

But deaths have declined dramatically since providers began routinely treating children with sickle cell disease with the antibiotic penicillin to help prevent infections. Affected children should receive penicillin twice daily between the ages of 2 months and 5 years .

All states now screen newborns for sickle cell disease as part of a panel of newborn screening tests. Early identification of affected babies alerts health care providers to begin treatment before dangerous infections occur.

It is important for babies and children with sickle cell disease to be given regular childhood vaccinations. The Hib Hemophilus influenzae vaccine and the pneumococcal vaccine (Prevnar) help protect against potentially life-threatening bacterial infections. These vaccines are recommended for all babies starting at months of age. Children with sickle cell disease should be given additional vaccinations, including:

Flu shot: This should be given every year, beginning at 6 months of age.Pneumococcal vaccine: This protects against additional types of bacteria. It is given at 2 and 5 years of age.Meningococcal vaccine: This vaccine, which protects against meningitis, is given after age.

Pain episodes: These are the most common symptom of sickle cell disease. Some affected individuals have one or fewer pain episodes a year, while others may have 15 or more. Pain episodes usually last a few hours to a few days, but they may sometimes last for weeks. Pain can occur in any organ or joint in the body, wherever sickle-shaped cells pile up and block blood vessels.

Mild pain episodes can be treated at home with over-the-counter pain medications (such as acetaminophen and ibuprofen) and heating pads. But some pain episodes may be severe and need to be treated in the hospital with strong pain-killing drugs.

The following steps may help prevent pain episodes in some affected individuals:

       -Drink plenty of fluids.

       -Avoid getting too hot or too cold.

       -Avoid places with high altitudes where oxygen levels are low.

       -Avoid extreme exercise.

       -Limit emotional stress.

Severely affected adults can take a drug called hydroxyurea. A 1995 study reported that treatment with hydroxyurea reduces the number of pain episodes in severely affected adults by about 50 percent. A 2003 study that followed the same patients for nine years found that treatment with hydroxyurea reduced deaths by 40 percent.

Some studies have found that hydroxyurea is effective and well tolerated in children in the short term. However, the drug is not yet routinely recommended in children because it is not known whether it has any adverse effects on growth and development. Researchers continue to study the long-term safety of the drug in children.

Hand-foot syndrome: Hands and feet may swell when small blood vessels become blocked. This may be the first symptom of sickle cell disease in babies, who also may develop a fever. It usually is treated with pain medication and fluids.

Stroke: A stroke can occur when sickle-shaped cells block a blood vessel in the brain. About 10 percent of children with sickle cell disease have a stroke. Stroke can lead to lasting disabilities, including learning problems.

Providers can sometimes identify children who are at increased risk for stroke using a special type of ultrasound examination. In some cases, a provider may recommend regular blood transfusions to help prevent a stroke.

A 1998 study found that regular transfusions greatly reduce the risk of a first stroke in high-risk children with sickle cell disease. Regular transfusions also reduce the risk of another stroke in children who already have had a stroke. A recent study showed that this treatment must be continued indefinitely because when treatment is stopped, a high risk of stroke returns. Unfortunately, regular transfusions pose some major risks, including a potentially fatal buildup of iron in the body. Children who receive regular transfusions must undergo treatment aimed at reducing iron levels.

Splenic crisis: The spleen is an organ that removes worn- out red blood cells and helps fight infection. In sickle cell disease, the spleen may become dangerously enlarged because it is clogged up with abnormal red blood cells. Symptoms include pain on the left side of the abdomen, weakness and rapid heart rate. This condition is treated in the hospital with blood transfusions. If the condition recurs frequently, the provider may recommend regular blood transfusions or removal of the spleen.

Acute chest syndrome: This is similar to pneumonia, with symptoms such as difficulty breathing, chest pain and fever. It can be caused by an infection or by blocked blood vessels in the lung. This potentially life-threatening disorder should be treated in the hospital. Treatments may include antibiotics, blood transfusions, pain medications, oxygen and medicines that help open up blood vessels and improve breathing.

Vision problems: When tiny blood vessels in the eye become blocked with sickle-shaped cells, vision problems and even blindness can result. Some individuals with sickle cell disease may need regular eye exams. When eye problems occur, laser treatment often prevents further vision loss.

Slow growth: Children with sickle cell disease tend to grow slower than normal and enter puberty later than other children due to anemia.

 What are signs and symptoms of sickle cell disease?

There are many symptoms for sickle cell. Individuals with sickle cell may not experience all of these symptoms. The symptoms include: family history of sickle cell anemia, fatigue, breathlessness, rapid heart rate, delayed growth and puberty, susceptibility to infections, ulcers on the lower legs (in adolescents and adults) jaundice, attacks of abdominal pain, weakness, joint pain, fever, vomiting, bloody (hematuria) urination, excessive thirst, excessive penis pain, priapism, chest pain and decreased fertility.

Symptoms may not appear until 4 months after birth and are most severe during an acute episode.

How long does a person whit sickle cell anemia disease live?

In the past, people with sickle cell disease rarely lived beyond age 20, but today they usually live well past age 50. It can't be cured and patients should avoid strenuous activities that reduce the amount of oxygen in their blood. They should also get all their immunizations. These things can increase their lifespan.

Can people whit sickle cell anemia live a product life?

Yes. But like all patients with chronic disease, sickle cell patients are best managed in a comprehensive multi-disciplinary program of care and a strong extended support system.

Are people of African descent only group affected?

No. It is also present in Portuguese, Spanish, French Corsicans, Sardinians, Sicilians, mainland Italians, Greeks, Turks and Cypriots. Sickle cell disease also appears in Middle Eastern countries and Asia. Perhaps, Sickle cell disease is the most common single gene disorder in black Americans, affecting approximately one in 375 persons of African descents.

How is a sickle cell anemia treated?

Sickle cell anemia has no widely available cure. However, treatments can help relieve symptoms and treat complications. The goals of treating sickle cell anemia are to relieve pain; prevent infections, eye damage, and strokes; and control complications (if they occur).

Blood and marrow stem cell transplants may offer a cure for a small number of people who have sickle cell anemia. Researchers continue to look for new treatments for the disease.

Is there a cure?

There's no cure for most people with sickle cell anemia. However, treatments can relieve pain and help prevent further problems associated with sickle cell anemia.

What is the future of sickle cell anemia treatment?

Bone marrow transplantation has been shown to provide a cure for severely affected children with sickle cell disease. Although many of the risks of this procedure have been reduced, it still is not entirely without risk. In addition, the marrow must come from a healthy matched sibling' donor, and only about 18 percent of children with sickle cell anemia are likely to have a matched sibling. Researchers are working on techniques to further reduce some of the risks of bone marrow transplantation for patients with sickle cell disease.

The ultimate cure for sickle cell anemia may be gene therapy. In sickle cell anemia, the gene which switches on production of adult hemoglobin shortly before birth is defective. Two approaches to gene therapy are being explored. Some scientists are looking into whether correcting this gene and inserting it into the bone marrow of people with sickle cell anemia will result in the production of normal adult hemoglobin. Others are looking at the possibility of turning off the defective gene and simultaneously reactivating another gene that turns on production of fetal hemoglobin. In both cases, the research is at a very early stage. Progress is being made, however, and there is a real possibility of an eventual clinical cure for sickle cell anemia.

How is sickle cell anemia detected?

Early diagnosis of sickle cell anemia is critical so that children who have the disease can receive proper treatment. A simple, inexpensive blood test for sickle cell disease on all newborn infants is done. This test is performed at the same time and from the same blood samples as other routine newborn screening tests. Hemoglobin electrophoresis is the most widely used diagnostic test.

If the test shows the presence of sickle hemoglobin, a second blood test is performed to confirm the diagnosis. These tests also tell whether the child carries the sickle cell trait.

How can a patient with sickle cell anemia disease, as well as their family and friends be helped whit coping?

Sickle cell patients and their families may need help in handling the economic and psychological stresses of coping with this serious chronic disease. Sickle cell centers and clinics can provide information and counseling on handling these problems. Parents should try to learn as much about the disease as possible so that they can recognize early signs of complications and seek early treatment.

Is it possible detecting sickle cell anemia disease in an unborn baby?

Yes. By sampling the amniotic fluid or tissue taken from the placenta, doctors can tell whether a fetus has sickle cell anemia or sickle cell trait. This test can be done as early as the first trimester of pregnancy.

What should future parents know?

People who are planning to become parents should know whether they are carriers of the sickle cell gene, and, if they are, they may want to seek genetic counseling. The counselor can tell prospective parents what the chances are that their child will have sickle cell trait or sickle cell anemia. Accurate diagnostic tests and information are available from health departments, neighborhood health centers, medical centers and clinics that care for individuals with sickle cell anemia.

Bibliography:

http://www.fbhc.org/Patients/Modules/sicklecell.cfm

http://www.nhlbi.nih.gov/health/dci/Diseases/Sca/SCA_WhatIs.html

http://www.sicklecelldisease.org/about_scd/index.phtml


http://www.aafp.org/afp/20000901/1013.html

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http://www.mayoclinic.com/health/sickle-cell-anemia/DS00324/DSECTION=symptoms

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