Acute Chest Syndrome and Sickle Cell Disease

Acute chest syndrome (ACS) is a common and severe complication of sickle cell disease (SCD). It happens when blood flow to the lungs is blocked and usually follows an acute pain crisis. ACS episodes can also be triggered by infections or asthma. ACS episodes are life-threatening and must be treated immediately in a hospital.

Symptoms of an ACS episode are similar to pneumonia. Prevention usually involves hydroxyurea or blood transfusions. Treatment must be done immediately and usually includes pain control, increased fluids, and oxygen therapy.

What is acute chest syndrome?

Acute chest syndrome is a broadly defined complication where a substance other than air is present in a section of the lung. It is a very serious condition that should be treated immediately in a hospital. In fact, ACS is the second-most common reason that people with SCD visit the hospital. It is also a leading cause of death.^1-3

About 50 percent of people with SCD will have an episode of ACS. It is most common among people with sickle cell anemia (HbSS) and sickle beta zero thalassemia.⁴

ACS severity increases with age because of a higher risk of arteries clogged by bone marrow and fat. In adults, more than 10 percent of cases are fatal or cause neurological damage. Adults are more likely to require a ventilator, have a longer hospital stay, and die because of ACS than children.^5,6

About 20 percent of adults with a history of ACS can experience a rapid type of ACS. This can cause quick respiratory failure and multi-organ failure, leading to kidney and liver damage. Repeated episodes of ACS can also lead to other long-term lung complications, such as pulmonary hypertension. This is a high blood pressure in the blood vessels from your heart to your lungs.^7,8

Why does sickle cell disease cause this?

People with SCD experience episodes of ACS when sickle cells block blood vessels in the lungs. This can damage the lungs because of a lack of oxygen. Blocked blood flow also leads to acute pain episodes. This is why 78 percent of ACS episodes follow acute pain crises, usually 2 to 3 days after hospitalization for pain.⁹

During SCD pain crises, bone marrow and fat are often released into the bloodstream. This can block blood flow to the lungs, leading to a condition called pulmonary embolism. Fat embolism causes 44 to 77 percent of ACS episodes in adults.^5,10

Infection and asthma are common triggers of ACS, especially in children. Other things that can affect air inhalation also may trigger ACS.^6,11

What are the symptoms?

Symptoms of ACS tend to be more severe for adults than for children with SCD. Adults experiencing an ACS episode often experience:⁶

• Chest pain
• Fever
• Cough
• Arm and leg pain
• Rib and sternal pain
• Shortness of breath

Adults with SCD who are showing these symptoms may also have pneumonia. Treatment for ACS may include antibiotics to address underlying infections.¹²

How is it prevented and treated?

Hydroxyurea and chronic transfusions may decrease the frequency of pain crises and ACS episodes. In people with sickle cell anemia or sickle beta zero thalassemia, hydroxyurea is the first therapy used to prevent these events. Doctors will then start chronic transfusion therapy if hydroxyurea is not working. L-glutamine may also decrease the rate of ACS episodes, but is not as effective in adults.^10,13

Asthma and lung disease increase the severity and frequency of ACS episodes. Children and adults with SCD should be regularly screened for lung function to detect these risk factors.²

Treatment of ACS usually involves some combination of:¹⁰

• Pain control with opioids
• Increased fluid intake by mouth or IV
• Simple or exchange blood transfusion
• Bronchodilators, especially in adults with asthma
• Antibiotics, especially in children
• Oxygen supplementation
• Steroids