What Is Sickle Cell Disease?

Red blood cells perform one of the most important tasks in the human body. The donut-shaped cells carry oxygen through blood vessels, delivering it to the rest of the body.

Sickle cell disease, a group of inherited blood disorders, can keep red blood cells from performing that job.

The disease, which is present at birth, causes a mutated form of hemoglobin to be produced. The defective hemoglobin can cause red blood cells to form a sickle, or C, shape. Affected cells can burst as they move through blood vessels. Or they can stick to blood vessel walls, causing blockages that affect the delivery of oxygen.

Sickle cell disease can cause symptoms such as severe pain, organ damage, and other complications.

“The disease can be a high burden and significantly impact the quality of life, right from childhood,” says Enrico Novelli, MD, a hematologist and oncologist and medical director of the UPMC Adult Sickle Cell Disease Program.

About 100,000 Americans have sickle cell disease.

What Causes Sickle Cell Disease?

Sickle cell disease is caused by a mutation in a person’s hemoglobin, the protein that helps red blood cells carry oxygen through the body. Abnormal hemoglobin molecules can bind together to form elongated, rod-like structures that can deform the red blood cell itself into a sickle (or C) shape.

The abnormal hemoglobin that causes sickle cell disease is known as hemoglobin S.

For a child to be born with sickle cell disease, at least one parent must have hemoglobin S and the other must have either hemoglobin S or another abnormal type of hemoglobin.

If both parents have hemoglobin S, the child has the most common and most severe type of sickle cell disease, known as sickle cell anemia.

If one parent has hemoglobin S and the other has normal hemoglobin, their child will be born with sickle cell trait. Children born with sickle cell trait generally live normal, symptom-free lives, but carry the risk of passing sickle cell disease to their children.

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Who Is at Risk of Sickle Cell Disease?

Black Americans are most at risk of developing sickle cell disease. According to the Centers for Disease Control and Prevention, the disease occurs in about 1 out of 500 Black American births in the United States. It also occurs in about 1 of 36,000 Hispanic-American births.

Other demographics more at risk include people whose ancestry comes from Indian, Mediterranean, Latin American, and Middle Eastern heritages.

Worldwide, millions of people have sickle cell disease – particularly those in lower-income regions such as India and sub-Saharan Africa. That figure could rise significantly as newborn screening becomes more available in those parts of the world, Dr. Novelli says.

How Is Sickle Cell Disease Diagnosed?

Sickle cell disease usually is diagnosed at birth in the United States. All 50 states and the District of Columbia require sickle cell disease screening for newborns.

As part of the screening process, doctors perform a blood test after collecting blood from the baby’s heel. They can determine whether the baby has sickle cell disease or sickle cell trait from the hemoglobin present.

If doctors do diagnose sickle cell trait or disease, they inform the parents and explain the results.

Sickle cell disease also can be diagnosed before birth. Doctors test a sample of the amniotic fluid for the sickle hemoglobin gene.

It’s important to diagnose sickle cell disease at birth because symptoms generally don’t present until the child is six months of age.

“If you wait for the children to have symptoms, it may be too late and some of them may have sepsis and die,” Dr. Novelli says. “That’s because by six months of age we start producing more adult hemoglobin (which is abnormal in people with sickle cell disease) that fetal hemoglobin.”

What Are the Symptoms of Sickle Cell Disease?

The most common symptom of sickle cell disease is pain. People with sickle cell disease can experience episodes of severe acute pain in the bones and joints.

“It starts from the time they’re children,” Dr. Novelli says. “The pain is because of blockage of small vessels in the bones.”

Other symptoms of sickle cell disease include:

  • Fatigue.
  • Dizziness.
  • Headaches.
  • Cold hands and feet.
  • Jaundice.
  • Pale skin and mucous membranes (inside the nose, mouth, and elsewhere in the body).
  • Dactylitis (swelling of hands and feet).
  • Dark urine.
  • Stunted growth.

Many of these symptoms are related to anemia. Sickle cell anemia is the most common form of the disease.

What Are the Complications of Sickle Cell Disease?

Many other serious medical conditions are related to sickle cell disease. These can occur with or without treatment:

  • Stroke: “Stroke is a devastating complication that normally occurs in older adults,” Dr. Novelli says. “However, this is one of the few diseases where stroke occurs in children.” Strokes can occur when sickle cells block a blood vessel in the brain, or when a blood vessel in the brain ruptures.
  • Pulmonary hypertension: Sickle cells cause blood vessels in the lung to narrow, making it more difficult for the heart to pump blood inside the lungs. Symptoms include fatigue and shortness of breath.
  • Acute chest syndrome: A serious lung injury caused by the blockage and leakage of blood vessels in the lung. Symptoms include chest pain, shortness of breath, and fever. Permanent lung damage is possible with multiple episodes.
  • Priapism: Prolonged, painful erections caused when sickle cells interrupt blood flow. It can lead to tissue damage and impotence.
  • Splenic crisis: Sickle cells can block the spleen, which then can become enlarged and cause severe abdominal pain. The spleen can either swell full of blood or become damaged or dead tissue. This puts a person more at risk of blood infections.
  • Leg ulcers: Occurring on the lower leg, these can cause severe pain and take very long to heal.
  • Organ failure: Sickle cell disease can cause any organ to receive less oxygen because of affected red blood cells, leading to possible damage.
  • Vision loss: Sickle cells can block blood vessels in the eye, damaging the retina and potentially causing vision problems or blindness.
  • Infection: People with sickle cell disease are more prone to infections, especially with spleen damage. Pneumonia is a leading cause of death of infants and children with sickle cell disease, according to the CDC.
  • Avascular necrosis: Damage or death of the hip bone because of poor blood flow.
  • Deep vein thrombosis: A serious, potentially life-threatening blood clot in a deep vein, usually in the leg.
  • Pulmonary embolism: A serious, potentially life-threatening blood clot in the lungs.
  • Gallstones: Sickled red blood cells have a shorter lifespan than typical. Their continued destruction can help form gallstones, which can migrate and block the bile duct, leading to severe abdominal pain.
  • Cerebral ischemia: sickle cell disease can restrict blood flow to the brain, causing tissue damage in the brain.
  • Cognitive impairment: Developmental delays and decreased cognitive function are possible for children with sickle cell disease because of blockage of oxygen to the brain.
  • Delayed growth: Sickle cell anemia can cause delayed growth or delayed puberty in children.

Can Sickle Cell Disease Be Cured?

Bone marrow or stem cell transplants can cure sickle cell disease. These procedures take healthy cells from a donor and transplant them into a recipient whose bone marrow isn’t working correctly.

However, these transplants also require a strong match between donor and recipient and carry significant risks, including death.

Dr. Novelli says gene therapy – replacing the sickle cell gene with a healthy one or introducing a gene that makes the disease less severe – is in clinical trials.

If a cure is not possible, there are treatments to help you manage sickle cell disease:

  • Transfusions: Blood transfusions can be used to reduce the risk of stroke in children, reduce the risk of another stroke of someone who already had one, or lessen complications of the disease. Red blood cell transfusions can help increase the number of healthy red blood cells.
  • Hydroxyurea: Originally a chemotherapy drug, this can lessen red blood cells sickling, cut down on pain episodes, and reduce inflammation.
  • Endari (L-glutamine): This medication makes red blood cells more flexible, cutting down on their chances of getting stuck in blood vessels.
  • Adakveo (crizanlizumab): This medication prevents the blood cells from adhering to blood vessels and cause blockages.
  • Antibiotics: These reduce the risk of infection.
  • Pain relievers: From over-the-counter options to stronger medications like opioids, these can help lessen pain for people with sickle cell disease.
  • Iron chelators: These medications reduce the overload of iron that occurs after many blood transfusions

People with sickle cell disease also can manage their condition by living a healthy lifestyle, including diet and exercise and good hydration. They should receive regular follow-up care with their doctor, stay up to date on vaccinations, and take vitamins and antibiotics. They also should avoid situations that can trigger sickle cell complications, including extreme temperatures, dehydration, very high altitude, low humidity, and intense emotional stress.

Most pregnant women with sickle cell disease do well during pregnancy and deliver healthy babies, but they are best served in a specialized maternofetal clinic.

How Can UPMC Help People With Sickle Cell Disease?

UPMC can treat people with sickle cell disease from birth through adulthood.

Both the UPMC Children’s Hospital Sickle Cell Program and the UPMC Adult Sickle Cell Program at UPMC Hillman Cancer Center have hematologists dedicated primarily to sickle cell disease. There also is a multidisciplinary team of doctors, advanced practice providers (physician assistants and nurse practitioners), social workers, psychologists, psychiatrists, nurses, research personnel and more.

UPMC has opened more than 20 studies, Dr. Novelli says, including several clinical trials.

“There is really a plethora of options for our patients, and we’re well-positioned to take advantage of all the new and upcoming treatments of sickle cell disease,” he says. “This is a time of great hope for sickle cell disease because there is a great interest at all levels, from professional organizations to pharmaceutical companies to policymakers, and there are some major breakthroughs in new therapeutics.”

Editor's Note: This article was originally published on , and was last reviewed on .

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