JACKSONVILLE, Fla. - Days after a 13-year-old collapsed during basketball tryouts, we’re learning more about the condition authorities say led to her death.

Preliminary autopsy results show Paris Byrd had Hypertrophic Obstructive Cardiomyopathy.

“The heart muscle over time thickens,” Dr. Sabrina Phillips, a cardiologist with the Mayo Clinic, said of the condition. “The interaction while the heart is squeezing and the geometry of the heart wall itself result in an obstruction.”

Dr. Phillips said about 1-in-500 people are affected by some form of Hypertrophic Cardiomyopathy, although not all cases cause obstruction of blood flow. However, both the obstructive and non-obstructive forms increase susceptibility to abnormal heart rhythms that can be deadly.

“These things are scary but thankfully serious consequences are very, very rare,” Phillips said.

University of North Florida sophomore and Jacksonville native Joe Meyer knows the danger firsthand. He was diagnosed with Hypertrophic Obstructive Cardiomyopathy when he was 14 years old.

He was getting a sports physical to play baseball and football when the doctor heart a heart murmur.

“He said that he didn’t want to clear me until I got it checked out further,” Meyer said.

Further tests and exams led to the diagnosis. Because the condition is most dangerous during exercise, Meyer was told he could no longer play sports.

“I was completely restricted on all physical activity,” he said.

After years of medicine and an open-heart surgery, Meyer said he’s now able to do light exercise. He volunteers with the American Heart Association to help spread awareness.

“It’s really just a blessing that I was about to catch it,” he said.

While the condition rarely shows symptoms, Phillips said it is genetic so people with it should have family members screened over the years because the muscle thickens over time.

For families where there is no known history, there are a few things to look out for.

“If they’re complaining of shortness of breath with exertion and certainly if anyone ever faints with exertion,” Dr. Phillips said. “Not fainting by itself like when you’ve been standing at church or standing for a long time, but we’d be worried about fainting with exertion. And that should prompt another evaluation by a physician.”