The onset of Kawasaki Disease is marked by a sudden high fever that lasts for at least 5 days. This is accompanied by extreme irritability - more than would be expected from the fever alone.

Other symptoms associated with Kawasaki Disease are rashes and/or swelling that affect the extremities (feet and hands) as well as the groin area, mouth, and eyes. There may also be swelling of the glands and lymph nodes. The lips may become cracked and bleed and the tongue becomes reddened. Also, the patient may have a stiff neck, swollen gall bladder, and abdominal pain as well as joint pain and peeling skin on the feet and hands.

The cardiac effects of this disease consist of the development of myocarditis (an inflammation of the heart muscle) and coronary aneurysms, or swellings, that develop on the coronary arteries. (The coronary arteries are the large vessels on the surface of the heart that arise from the root of the aorta and supply the heart muscle with oxygen-rich blood.) Coronary aneurysms are the most devastating result of Kawasaki's disease occurring in 20% of untreated children and <5% of treated children. Most of the aneurysms form in the proximal coronary arteries (near their points of attachment to the aorta). They may cause a heart attack if they become blocked by a blood clot.

If these aneurysms do not disappear after the patient has recovered from Kawasaki Disease, or if they result in weak areas in the arteries, they may cause problems later in life. For example, there may be thickening or obstruction of the coronary artery walls because of calcification or the early development of atherosclerosis (deposition of fatty materials).