"Seizures are not part of Kawasaki disease," the New York Daily News quoted Dr. Stanford Shulman, a specialist in the disease at Northwestern University's Feinberg School of Medicine, as saying.
"If a teenager had a seizure and died, that would not commonly be due to Kawasaki disease," the expert added.
Kawasaki disease cleads to fever, rash, red eyes and swollen hands and feet.
The sickness is more common in young boys, and its cause is controversial.
While some, like Jett's actress mother Kelly Preston, think that environmental toxins trigger the symptoms, others blame a virus.
Kawasaki can lead to blood clots and heart attacks later in life if left untreated.
"Nowadays, no more than 2 or 3 percent of cases develop significant coronary artery abnormalities, so deaths are rare, but they do occur," Shulman said.
Studies conducted in recent past have suggested that seizures may occur in kids suffering from acute Kawasaki disease.
Jett's parents have revealed that their child was rushed to hospital when he was just 2, and diagnosed with the disease.
His mother Kelly Preston revealed that the boy recovered following a detoxification program, though he still had "allergies."
Police in the Bahamas said on Friday that they were told Jett had a history of seizures.