The Story of Sickle Cell Disease

From height, to dimples, to hair color, our genetics can define much of our physical identity. These inherited traits affect not only our looks, but also our health. Sickle cell disease (SCD) for example, is one of many inherited disorders that can be passed down through genes from parents to their child. However, unlike a certain eye color, SCD can have a lifelong health impact.

SCD typically results from each parent passing on an abnormal hemoglobin gene producing Hemoglobin S (or one parent passing on Hemoglobin S and the other parent passing on a different abnormal hemoglobin gene such as Hemoglobin C or one associated with beta-thalassemia).  Having one abnormal hemoglobin gene that produces Hemoglobin S makes a person a sickle cell disease carrier or a sickle trait carrier but they do not typically experience symptoms of the disorder.  According to the Sickle Cell Disease Association of America (SCDAA), there are approximately 70,000 -100,000 Americans living with SCD. Approximately 1,000 babies are born with the disease every year.   While it may occur in any ethnicity, in the United States it affects 1 in 500 African Americans and 1 in 1,000 to 1 in 1,400 Hispanic Americans1.

SCD symptoms are caused by abnormally shaped red blood cells, which have a crescent, or sickle-shaped appearance. Normally blood cells are round and flexible, easily passing through blood vessels to carry oxygen throughout the body.  Sickle cells are rigid and prone to getting stuck and blocking blood flow through the body’s small blood vessels.  When blood does not reach a certain part of the body, it is deprived of oxygen and the tissue begins to break down and become damaged. Due to the blockages caused by the sickled red blood cells, individuals with SCD often experience painful episodes called pain crises in the affected body parts (i.e. arms, legs, chest and abdomen), according to the SCDAA. Such a blockage can also cause long-term damage to the lungs, kidneys, liver, brain and spleen, making those with the disease especially vulnerable to serious bacterial infections.

While normal red blood cells last 90 to 120 days, sickle cells only last 10 to 20 days.  This leads to a condition called anemia, which is having less red blood cells than normal.  Over time, this can cause paleness, shortness of breath, poor growth and an increased likelihood of exhaustion, according to the National Heart, Lung and Blood Institute (NHLBI).

Health complications from SCD can be challenging and there are several treatment options available.  Doctors specializing in SCD can recommend targeted and customized treatments. A patient’s options may include medications to manage infections and pain, regular blood transfusions and, for some patients, a bone marrow transplant.  Currently, the life expectancy of a person with SCD in the United States is 40-60 years according to NHLBI.  The only cure is a hematopoietic stem cell transplant (HSCT), which requires a relative that is a genetic match to donate to them.

While the thought that what is in your genes may be harmful to your future family may be distressing, understanding the possible genetic outcomes can help carriers make informed decisions. When both parents carry the sickle cell trait (one copy of the abnormal hemoglobin gene) or one parent carries the sickle cell trait and the other parent carries a different abnormal hemoglobin, the child has a 25 percent chance of being affected by SCD. There is a 50 percent chance that a child with carrier parents will be born with the sickle cell trait (SCT) and the child will simply be a carrier of the disease, or that the child will be a carrier of the abnormal hemoglobin in the parent, and will not experience any adverse symptoms.   There is also a 25 percent chance that a child with carrier parents will not inherit any sickle cell or abnormal hemoglobin genes and hence be unaffected (and not a carrier).

As with any disease, early diagnosis is key. Genetic screening is the easiest way to learn your odds of passing on SCD and start protecting the health of your child. For more information on sickle cell disease and how to test for it, you can visit Good Start Genetics, as well as the National Heart, Lung and Blood Institute and sicklecelldisease.org.

References: 1. http://ghr.nlm.nih.gov/condition/sickle-cell-disease

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