What is Kawasaki disease?

Kawasaki disease is an uncommon but important cause of fever in children. It was first noticed in Japanese children following World War II. While it is more common among the Japanese, we now know that it occurs in all racial groups, primarily in children under 5 years of age. Sometimes Kawasaki disease appears in clusters of children, suggesting that infectious organisms may trigger the condition.

Kawasaki disease is an inflammation of the child's blood vessels. The most important blood vessels involved are those of the heart, including the coronary arteries. Kawasaki disease has become the most common cause of heart disease in children born without birth defects. If Kawasaki disease is not recognized and appropriately treated within 10 days, the risk for permanent heart damage increases. Children can die from heart problems during this illness. They can also die from heart attacks later in childhood or as young adults. Early treatment is effective in preventing this, but first Kawasaki disease must be recognized.

There is no specific blood test for Kawasaki disease. The diagnosis is based on symptoms. The disease is also called mucocutaneous lymph node syndrome because the classic symptoms are in the mucus membranes, skin, and lymph nodes. At an international symposium in Tokyo 10 years ago, expert participants agreed on a definition for Kawasaki disease (Pediatric Infectious Disease Journal 1989; 8:663):

A. Fever lasting for at least 5 days

B. Presence of any four of the following five conditions:

1. Red eyes without discharge
2. Changes of the mucus membranes of the mouth, including red throat or red and/or dry and cracked lips, or strawberry tongue (a white coat on the tongue through which swollen red bumps protrude).
3. Changes of the hands or feet, such as swelling and/or redness and/or peeling of the skin, usually beginning around the nails.
4. Rash on the trunk. May take many forms, but without blisters. Perhaps also present on the limbs or face.
5. Swollen neck lymph node or nodes.

C. Illness not explained by another known disease.

Almost all children with Kawasaki disease are quite irritable. Because blood vessels throughout the body can be affected to varying degrees, many other symptoms might or might not be seen. These include diarrhea, vomiting, abdominal pain, cough, runny nose, headache, arthritis, burning urination, mouth sores, sensitivity to light, nerve weakness, confusion, or seizures.

To make the situation more confusing, many children with true Kawasaki disease do not fulfill all of the classic criteria. We call this ‘incomplete’ or ‘atypical’ Kawasaki disease. We know that some children have it because they go on to develop the coronary artery aneurysms of classic Kawasaki disease, even though they do not have all of the other symptoms.

These cases without all of the classic diagnostic clues are most common in infants less than 1 year of age.