Kersey died yesterday at the age of 52.
Dr. Larry Lewman tells TMZ Sports ... "There was a blood clot in his left calf that broke loose and traveled to his lungs and clogged both his pulmonary arteries."
Dr. Lewman adds, "We're still gathering information, but it appears he had a surgical procedure recently. Anyone who is post surgical, who isn't moving around a lot, is at risk."
Several high-profile people have passed away from the same condition -- including Heavy D, Dennis Farina and reporter David Bloom.
Again, condolences go out to Jerome's family, teammates, and friends.
Update: Former Trail Blazers Head Coach Rick Adelman made this statement:
Jerome was a special person. I've known Jerome since he came into the league. How he earned his spot on our roster is an inspiring story and underscores just what a warrior he was. He never quit. He was someone you could count on every time he stepped on the court. He was just such a rock for those special Trail Blazers teams. He also cared about the community and was always giving back. My condolences go out to his family, friends and all those that knew and loved him.