John Travolta's lawyers, Michael Ossi and Michael McDermott, said Sunday Jett Travolta, the actor's 16-year-old son who died Friday, was on an anti-seizure medication called Depakote for several years, but the drug was suspended after it lost its effectiveness amid concern about side effects.

Jett apparently suffered from grand mal seizures, a type of epilepsy marked by convulsions and loss of consciousness, Ossi and McDermott said.

Click here to learn more about Jett's struggle with Kawasaki disease.

Jett, who had a history of seizures, was found unconscious in a bathroom at his family's home at the Old Bahama Bay resort on Grand Bahama Island on Friday morning.

He was pronounced dead after being taken by ambulance to Rand Memorial Hospital in Freeport and an autopsy to determine the cause of death is due to be performed in the Bahamas on Monday.

Ossi and McDermott said Jett had been suffering about one extremely serious seizure a week.

VIDEO: Click here to watch Dr. Manny discuss Jett's death on FOX & Friends.

Travolta and his wife, actress Kelly Preston, have said previously that Jett became very sick when he was a toddler and was diagnosed with Kawasaki disease, which leads to inflammation of the blood vessels in young children.

In a 2003 interview on the Montel Williams show, Preston talked about her son's struggle with Kawasaki disease. "It causes swelling in the organs, so your heart can swell, different important organs can swell," she said. "We thought at one point we were going to lose him."

Dr. Scott Alenick, a pediatric cardiologist in New Jersey, told FOXNews.com in an interview last year that Kawasaki disease is a condition that affects children, especially boys under the age of 5, and causes aneurysms and blockages in the blood vessels.

"We usually see it in the winter, but it can occur year-round,” Alenick, who has treated hundreds of cases of Kawasaki disease, said. “It is very unusual to die from Kawasaki disease.”

According to the American Heart Association, more than 4,000 cases of the disease are diagnosed annually in the United States. It occurs more often in boys of Japanese and Korean descent, but has been identified in children of all ethnicities and races, Alenick said.

While the condition is not preventable, it is treatable with most children recovering from the disease. In fact, less than 1 percent of Kawasaki cases are fatal.

The danger of Kawasaki syndrome is that it can cause large aneurysms in the blood vessels that feed blood to the heart, said Alenick.

“Kawasaki doesn’t come in degrees of severity, but it varies in that it may cause no aneurysms, small aneurysms, moderate aneurysms or giant aneurysms,” he said. “Giant aneurysms are more common in babies. But it’s the aneurysms that form in the vessels and the arteries that feed the heart that have the potential to cause a fatal heart attack.”

The disease was first identified in Japan in 1967 by Dr. Tomisaku Kawasaki, and the cause of the illness is still unknown, Alenick said. There also is no blood test to identify the illness. Instead, patients are given a clinical diagnosis based on whether they display at least five of these six symptoms: a high fever that lasts for more than five days, red lips and tongue, swelling of the hands and feet, bloodshot eyes, rash and swollen glands.

Once a diagnosis is made, patients are given high doses of aspirin to control the inflammation and put on an IV drip consisting of gamma globulin. Once the initial inflammation is brought under control, most children are kept on a low dose of aspirin to prevent clots and aneurysms from forming in the veins, Alenick said.

Ossi and McDermott did not immediately return calls from Reuters on Sunday seeking comment. Travolta's publicists have declined to comment on autopsy or funeral plans for the actor's teenage son.

Travolta and Preston also have an 8-year-old daughter, Ella.

The Associated Press and Reuters Health contributed to this report.