In 2003, Kelly Preston told Montel Williams that when Jett was 2, he became ill with flu symptoms, including fever, rashes and swollen lymph nodes, before a doctor diagnosed him with Kawasaki disease.

CNN: Actors' son Jett Travolta dies at 16

The causes of Kawasaki disease are unknown.

CNN: Actors' son Jett Travolta dies at 16

Jett Travolta had a developmental disability that his parents, John Travolta and Kelly Preston, have linked to Kawasaki disease, an inflammatory disorder of the artery walls that most commonly occurs in young children and can lead to heart disease.

CNN: Actors' son Jett Travolta dies at 16