Allegheny County Medical examiner Dr. Karl Williams said Kyle Chase Johnson, 23, who died while running Pittsburgh's half-marathon Sunday, had an inherited abnormality of the coronary artery system.
Williams said Johnson, who played football for North Allegheny High School and graduated one year ago from Penn State, had a rare congenital defect that caused a coronary artery to take "an abnormal pathway around the aorta."
"The coronary arteries supply oxygen to the muscles of the heart," Williams said in a statement. "Defects of this nature, although rare, are known to be associated with sudden unexpected death."
Williams said these defects are nearly impossible to detect.
"These are rare abnormalities," he said. "There would be no economical, safe way to screen everybody for it."
Johnson was an interior defensive lineman for the North Allegheny Tigers.
"Kyle was an outstanding young man," said Bob Bozzuto, North Allegheny's Athletic Director. "While attending North Allegheny, he was an outstanding, dedicated student athlete."
"Kyle made a difference to our football team. We would be different without him. We are a better team because he was part of us," North Allegheny football coach Art Walker told WTAE-TV. "There was never down time with Kyle. He was always just a great kid, smile on his face, always wanted to be a part of everybody."
Johnson had moved into an downtown Pittsburgh apartment with a long-time friend just a few weeks ago, the Pittsburgh-Post Gazette reported.
Mr. Johnson's mother, Mary Beth Deal, said Mr. Johnson was "on top of the world" after getting an accounting job at Deloitte & Touche.
"He was a wonderful, wonderful son," she told the Post-Gazette. "He loved to read, he was smart, he was kind and handsome."
Funeral arrangements are incomplete.
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