Diving into the Genetics of Sickle Cell Disease

The “Ask Dr. Kevin” series is brought to you by Pfizer Rare Disease in collaboration with the National Newspaper Publishers Association (NNPA) to increase understanding of sickle cell disease.

Dr. Kevin Williams is the Chief Medical Officer for Rare Disease at Pfizer. He pursued medicine after being inspired by his father’s work as a general practitioner in his hometown of Baton Rouge, Louisiana. Dr. Kevin is passionate about raising awareness and increasing understanding of rare diseases, such as sickle cell disease, in the African American community.

In recent years, genetics has become a hot topic in popular culture, frequently making news headlines and serving as a key theme in movies and TV shows—and for good reason: our genes are what make us unique.

Genes not only help to shape our tastes and preferences, but they also can influence our health. In some cases, our genes play silent roles within our bodies. In others, genes take on a more prominent role, even determining our likelihood of having specific diseases.

This brings me to sickle cell disease (SCD), a topic I am passionate about and have discussed in previous articles. In this article, I’d like to focus on the often under-recognized fact that SCD is a genetic disease and is inherited from the passing of the sickle cell gene from parent to child.

Not everyone who inherits the sickle cell gene has SCD. Only people who inherit the gene from both parents develop this condition. This is an important distinction, as a person who inherits the sickle cell gene from only one parent while inheriting a normal gene from the other will have sickle cell trait, and typically will live a relatively normal life. However, people with sickle cell trait have a 50% chance of passing the gene to their children.[1]

I’m here to answer some of the most common questions that I’m asked about the sickle cell trait and suggest available resources for additional information.

How prevalent is the sickle cell trait?

Research indicates that as many as 3 million Americans carry the sickle cell trait, primarily impacting African Americans. In fact, nearly 1 in 12 African Americans have the sickle cell trait.¹

Worldwide, more than 100 million people carry the sickle cell trait.[2] It is most prevalent among sub-Saharan Africans, Hispanics, South Asians, Caucasians from southern Europe, and people from the Middle East.¹

Are there complications with having the sickle cell trait?

The majority of people who carry the sickle cell trait do not experience complications. However, that is not to say that everyone with the trait remains symptom-free. Though rare, extreme conditions such as severe dehydration, high-intensity physical activity, and low oxygen environments (e.g.: high-altitude locations) can lead to serious health issues or even sudden death for individuals with the sickle cell trait.¹

How do you know if you have the sickle cell trait?

All it takes is a simple blood test to learn if you have the sickle cell trait. You can talk with your doctor or a health clinic about getting the test.

In the US, all newborns are screened for the sickle cell trait before they leave the hospital. The results are usually available at the child’s one-month appointment. I strongly encourage older children and adults who weren’t tested as newborns to consider getting the test.

Why is it important to know your sickle cell trait status?

Getting screened is extremely important. If you know you have the trait, you will be more likely to take precautions to avoid those extreme conditions I mentioned earlier, like severe dehydration, high-intensity physical activity, and low-oxygen environments (eg, high-altitude locations), which could potentially trigger the onset of symptoms.¹

For those considering having children, consulting a genetic counselor, who can help them better understand what it means to be a carrier of the gene and the chances of having a child with SCD or the trait, should be considered.

It is important for everyone, particularly African Americans, to know their status. I always say that knowledge is power when it comes to your health.

Where can you go to learn more?

• I encourage you to speak with your doctor about any concerns related to SCD and the sickle cell trait. There are also great resources out there to learn more: Head to com to find information and advice for patients and caregivers, search for healthcare professionals, and access community support and other resources.
• Review the US Centers for Disease Control and Prevention’s “Get Screened to Know Your Sickle Cell Status” to learn more about sickle cell testing.
• Contact national and/or local advocacy groups to learn more about genetic screenings that are offered in your area.

About Dr. Kevin Williams

Dr. Kevin Williams is the Chief Medical Officer (CMO) for Pfizer Rare Disease. In this role, he leads a Medical Affairs organization of approximately 150 medical colleagues around the globe supporting Pfizer’s efforts and portfolio in Rare Disease. Dr. Kevin joined Pfizer in January 2004 as a Director of Regional Medical & Research Specialist working in the HIV disease area. After moving into a Team Leader position in July 2005, he served in various leadership roles during his career at Pfizer. Dr. Kevin moved into his current Rare Disease CMO position in May 2016.

Dr. Kevin received his medical degree from the UCLA School of Medicine and is board certified in Internal Medicine. Following a 2-year fellowship in Health Services Research at UCLA and a brief academic career as an Instructor of Medicine at the UCLA School of Medicine, he spent 8 years in private practice caring for HIV-positive patients while maintaining an academic appointment at the UCLA School of Medicine as an Assistant Clinical Professor of Medicine. In addition to his medical degree, Dr. Kevin has a Masters in Public Health from the UCLA School of Public Health and a Juris Doctorate from Harvard Law School.

Keep up to date on Pfizer’s SCD efforts by visiting our page here. You can also follow Pfizer on Facebook and Twitter.      

[1] Centers for Disease Control and Prevention. What you should know about sickle cell trait.  https://www.cdc.gov/ncbddd/sicklecell/documents/SCD%20factsheet_Sickle%20Cell%20Trait.pdf. Accessed November 13, 2018.

[2] American Society of Hematology. Sickle cell trait. http://www.hematology.org/Patients/Anemia/Sickle-Cell-Trait.aspx. Published September 8, 2017. Accessed November 18, 2018.