Sickle Cell Disease

Sickle cell disease (SCD) is the most common inherited blood disorder in the US. It affects more than 100,000 people in the US and 20 million people worldwide. You have probably heard it called sickle cell anemia. It is a lifelong condition that can lead to multiple serious health problems.
 

What is sickle cell disease?

SCD is an inherited blood disorder that affects the hemoglobin found within red blood cells. Hemoglobin is the protein within the red blood cells that carries oxygen through the body.

Normal red blood cells are disc-shaped and very flexible. This flexibility allows them to move easily through the blood vessels, even tiny capillaries. SCD causes the red blood cells to be shaped like a crescent or "sickle". Unfortunately, these sickle-shaped cells are not flexible at all. They get caught in blood vessels and can cause a "log jam", blocking blood flow in arteries throughout the body.

How is SCD inherited?

For a person to have SCD, they must get one abnormal "sickle-cell" gene from each parent. If only one parent passes a sickle cell gene to the child, and they get one normal gene from the other parent, this is called "sickle trait". People with sickle trait will make both sickle hemoglobin and typical hemoglobin. They may have some sickle-shaped red blood cells, but most of their red cells will be normal shaped and they usually don't have symptoms of SCD.

In the US, SCD most commonly affects people of African, Mediterranean, and Middle Eastern descent.

What are the symptoms of SCD?

Symptoms usually start around 6 months of age, when the fetal hemoglobin is replaced by the hemoglobin being produced since birth. Symptoms vary somewhat and can change over time. Here are some of the symptoms and signs of SCD:

• Anemia -Sickle cells break apart easily and die. A normal blood cell will usually live for around 120 days, but a sickle cell usually only lives 10-20 days. This leads to a shortage of red blood cells (called anemia) because the body can't make blood cells fast enough to replace them.
• Fatigue - Caused by anemia, and inability to get enough oxygen to the body.
• Episodes of acute pain - Called pain crises, periodic episodes of extreme pain are a major symptom of SCD. It is caused by lack of blood flow to an area, like having a heart attack in your muscles or joints.
• Chronic pain - Intermittent lack of oxygen to tissues can cause damage to joints, bones, skin, and internal organs, including the heart. This can lead to chronic pain, usually starting in adolescence or early adulthood.
• Frequent infections - Your spleen helps protect you from infections. Sickle cells damage the spleen, leading to higher susceptibility to infections. People with SCD require more vaccines than most people to help prevent life-threatening infections.
• Delayed growth or delayed puberty - Red blood cells carry oxygen and nutrients, which are important for growth and development. This is delayed when you don't have healthy red blood cells.
• Vision problems - The sickle cells cause severe problems with the small arteries in the retina of the eye. This can lead to vision problems and even blindness.

What are the possible complications of SCD?

SCD can lead to a host of complications, which may be the result of acute blockage of blood flow, recurrent or chronic blockage of blood flow, or tissue damage resulting from this lack of blood flow. Complications can include:

• Stroke - Even in very young children, stroke can happen when a blood vessel in the brain is blocked by sickle cells.
• Acute chest syndrome - Chest pain, fever, and shortness of breath due to blockage in the blood vessels in the lungs or from lung infections.
• Pulmonary hypertension - High blood pressure within the blood vessels in the lungs is usually from chronic damage, so most often affects adults with SCD.
• Organ damage - Damage to organs including kidneys, liver, and spleen results from being deprived of oxygen. This can sometimes be fatal.
• Enlarged spleen - Can lead to spleen rupture, which is life-threatening.
• Blindness - From retina damage.
• Leg ulcers - Due to damage to skin.
• Gall stones and jaundice - Due to the high turnover of red blood cells, which causes high levels of bilirubin in the blood.
• Blood clots - Such as deep vein clots or lung clots, which may be fatal.
• Pregnancy complications - Including blood clots, high blood pressure, miscarriage, premature birth, or babies with low birth weight.
• Priapism - Men with SCD can have long-lasting, painful erections, due to the sickle cells blocking blood vessels in the penis. Over time, this can lead to impotence.

Next week we will continue our discussion of sickle cell disease by talking about how the disease is diagnosed and available treaments.

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Dr. Anita Bennett MD - Health Tip Content Editor