Victoria Gray, a 41-year-old woman from Mississippi was born with sickle cell disease, an often painful and debilitating condition.

The only current treatment for sickle cell anemia patients is a donor transplant that works for just 10% of patients.

People with sickle cell disease don’t make beta-hemoglobin—the protein that both makes your red blood cells nice and round and helps transport oxygen through your body.

Instead, they produce a faulty protein called hemoglobin S that changes the red blood cells’ chemistry and causes them to cave in on themselves and become rigid and sickle-shaped.

The hook-like cells are not nearly as efficient at transporting oxygen as their healthy, circular counterparts.

Instead, they get stuck in small blood vessels and breakdown prematurely, depriving tissues and organs of much-needed oxygen, leading to pain and extreme fatigue.

To try and treat it, doctors removed stem cells from Gray’s bone marrow and used CRISPR to tweak the DNA to turn on a specific protein that would allow for proper red blood cell production.

Gray is the first person in the U.S. to have her cells altered with CRISPR and the second globally.

Read more at Interesting Engineering and Popular Science.