Sickle-cell disease

Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at February 29, 2016
StartDiseasesSickle-cell disease

Sickle-cell disease or sickle-cell anemia is a condition wherein abnormal hemoglobin activity in the body's red blood cells causes these cells to distort shape and fail to carry out their duty of transporting oxygen throughout the body. This form of anemia is genetically inherited from one's parents.

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Definition & Facts

Sickle-cell disease is considered a blood disorder, although it is associated with the onset of many other afflictions such as chronic pain, severe infections and strokes. People diagnosed with sickle-cell disease generally are given a decreased life expectancy, although medical advances in treatment and diagnosis have extended the average lifespan of afflicted patients from around 15 years in the 1970s to 40-60 years in the present day.

Sickle-cell anemia is genetic and therefore not contagious. Almost 300,000 people are born with sickle-cell disease every year, with many of these people being of African origin. As of 2016, the scientific community has not cured sickle-cell disease; in fact, the only known cure for any sickle-cell disease is hematopoietic stem cell transplantation, which is a risky and controversial procedure.

Symptoms & Complaints

Most cases of sickle-cell anemia are diagnosed in infancy, and babies born in the United States and U.S. territories must be screened for sickle-cell disease at birth. If the diagnosis is not made immediately, symptoms will start to manifest when the baby is between four and six months old.

Symptoms include fatigue and anemia caused by a shortage of red blood cells; periods of intense pain, called pain crises, that may last a few minutes or even up to a few weeks; swollen hands and swollen feet caused by blood flow blockages; and frequent infections exacerbated by a weakened spleen.

Growth delays and vision problems are signs of sickle-cell anemia in small children. Older, undiagnosed people should contact their doctor if they experience any of the above symptoms as well as abdominal swelling, jaundice, pale nail beds or signs of a stroke.

Causes

Sickle-cell anemia is caused by a mutation in the beta globin gene that instructs the body in how to make hemoglobin. Hemoglobin is the red, iron-rich substance that allows red blood cells to carry oxygen throughout the body. Abnormal hemoglobin, called hemoglobin S, causes sickle-cell disease when it is inherited from both parents. People with only one Hemoglobin S gene are considered carriers of sickle cell trait, but they will rarely experience the health defects that those with two S genes will.

The sickle cell gene is passed from generation to generation in a process called autosomal recessive inheritance. This pattern of inheritance means that any two people who have a baby together while knowing that they both have sickle cell trait have a 25% chance of having a baby with sickle-cell disease.

Diagnosis & Tests

There are several tests that are used to diagnose the presence of sickle-cell diseases or the presence of hemoglobin S in babies and adults. The most common test is a basic blood test, in which blood is drawn from an arm vein and tested in a laboratory (blood is usually drawn from a finger, toe or heel of a baby).

This blood is tested for the presence of hemoglobin S, and also for the presence of other abnormal hemoglobin varieties such as hemoglobin C, Beta thalassemia, orhemoglobin E. If the first stage of the test concludes that the blood does contain traces of hemoglobin S, further tests are ordered to see whether the person has sickle-cell disease or is merely a carrier. If there are large amounts of hemoglobin S in the blood, the baby or adult has sickle-cell anemia or a related blood disease.

There are also prenatal tests that can determine if the baby has the sickle cell gene. These tests are performed by studying the amniotic fluid surrounding the embryo while it is in the womb. A tissue sample can also be taken from the placenta, which is the organ that connects the unborn baby's umbilical cord to the mother's womb.

Treatment & Therapy

The importance of childhood vaccinations grows exponentially for those with sickle-cell anemia, because run-of-the-mill infections can quickly spiral out of control. These essential vaccinations include those that prevent pneumococcus, influenza, and meningococcus.

Although experimental bone marrow transplants have been successful in the past, most conventional sickle-cell anemia treatment focuses on relieving symptoms, preventing excessive pain crises, and preventing infections and complications.

There are several other treatments that doctors commonly rely on including:

  • Regular blood transfusions, meant to increase the number of red blood cells in circulation
  • Regular administration of the antibiotic penicillin, meant to help fight certain infections
  • Regular administration of hydroxyurea meant to reduce the need for blood transfusions and the frequency of pain crises
  • Over-the-counter and prescription pain medication

There are other, more radical, treatments that are currently being tested by doctors. These include gene therapy, nitric oxide treatments, cholesterol-lowering statins, and drugs intended to boost hemoglobin production in fetuses.

Doctors also recommend several basic treatments that can be practiced at home. Taking folic acid supplements, maintaining a healthy diet, exercising regularly and avoiding high-altitude situations can help patients avoid further complications brought on by their sickle-cell disease.

Prevention & Prophylaxis

Unfortunately, because sickle-cell anemia is a genetic disorder, there are few steps that prospective parents can take to ensure that their offspring does not end up with the disease. People who carry the sickle-cell trait should see a trained genetic counselor before having children; this counselor can elucidate risks, suggest tests that should be taken, and propose alternative reproductive options.

Maintaining an open dialogue with both doctor and partner is very important: both parents should test their own blood for hemoglobin S and understand the risks inherent in a double-carrier pregnancy before attempting to conceive. Sickle-cell disease is no longer the death sentence that it once was, and it is always best to arm oneself with information.