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Sickle Cell — What Is It?

By Jon Mark Hirshon
MD, MPH, PhD, FACEP

I received the sad news last week that a colleague and a friend had died. Trevor was a great man. A hard working, caring and thoughtful leader dedicated to helping people with sickle cell disease.  Unfortunately, he also had the disease- something he lived with his whole life.

Sickle cell disease (SCD), while considered a rare disease, is the most common genetic blood disorder in the United States. It affects 90,000-100,000 Americans, primarily of African and Hispanic descent. Individuals from Mediterranean countries such as Turkey, Greece, and Italy, as well as from Saudi Arabia and India may also have it. As a genetic disease, it is not spread from one person to another, but it is passed from parents to their child. Globally, it estimated that over 310,000 children are born every year with SCD.

Frequently, patients with SCD come into my emergency department with severe pain. They have these episodes of severe pain because their blood cells flow poorly through the capillaries. These vaso-occlusive episodes (VOE) are the most common reason for emergency department visits. However, in addition to VOEs with severe pain, my patients with SCD can have multiple life and limb threatening problems, such as strokes and kidney failure. When their sticky red blood cells get caught in the lungs, it can cause part of the lungs to stop working. This is called “acute chest syndrome” and is the major cause of death in adults with SCD. These problems can hurt both children and adults. In the United States, SCD is a costly disease, with health care related cost estimated to be $488 million in 2004.

Healthy red blood cells usually move smoothly through the capillaries (small blood vessels) in the body to carry oxygen where it is needed in the body.  In patients with SCD, their red blood cells become hard, inflexible, sticky and look like a C-shaped farm tool called a “sickle”. These sickle-shaped cells are less able to carry oxygen and die earlier than normal cells, leading to low blood counts (anemia) and a constant need for more red blood cells.

As an inherited disease, both parents need to have the sickle hemoglobin gene to pass it on. Hemoglobin is the protein molecule oxygen in red blood cells. Many people may not know they have this gene, as patients with sickle cell trait (SCT) have one normal and one abnormal gene for hemoglobin. In most instances, patients with SCT have no symptoms. However, their children may have SCD if both parents pass on the sickle hemoglobin gene.

While there is no cure for SCD, there are medications to decrease the risk of major problems.  SCD patients can get vaccinated against pneumococcal disease and influenza, which decreases the likelihood of getting severe infections. They can also take a medication called hydroxyurea that helps to produce a special hemoglobin called hemoglobin F, which is normally only seem in young babies. Red blood cells with hemoglobin F are much better at carrying oxygen and moving through small blood vessels than the sticky sickle blood cells.

Research is ongoing to improve the care of patients with SCD. The hope is someday of finding a cure.  The American College of Emergency Physicians is actively involved in improving the care of SCD patients in emergency departments through the development and support of the Emergency Department Sickle Cell Care Coalition (EDSC3). EDSC3 provides a national forum dedicated to the improvement of the emergency care of patients with SCD in the United States. Its objectives are to promote quality, patient safety, communication, responsibility, and clarity in regards to the emergency care of patients with SCD.

About the Author: Dr. Jon Mark Hirshon is a member of ACEP’s Board of Directors.   He is also Professor, Department of Emergency Medicine and of Epidemiology and Public Health at the University of Maryland, School of Medicine.