THE THREE STAGES OF KD
Kawasaki disease is a self-limited illness, which means the symptoms go away on their own. However it may take 6-8 weeks for the symptoms to resolve and the laboratory results to return to normal, and the effects on the coronary arteries can last a lifetime. The illness can be divided into three stages: acute, sub acute, and convalescent phases.
THE ACUTE PHASE
The acute phase starts with fever, which lasts for at least 5 days (average of 11 days without treatment). Over the first week, the symptoms that comprise Kawasaki disease reveal themselves, but often one symptom appears as another disappears, making the diagnosis challenging, especially for children who see different physicians during the early days of their illness. An ultrasound of the heart (echocardiography or ECHO) is done at the time of diagnosis to look at the way the heart squeezes, and to get baseline measurements of the coronary arteries. Some children may have mild or moderately decreased heart output due to poor contraction of inflamed heart muscle; some may have a small amount of fluid around the heart (pericardial effusion). Very rarely, cardiac rhythm (electrical) disturbances may occur.
THE SUB ACUTE PHASE
The sub acute phase begins when the fever stops. However, many parts of the body are still affected by the disease. During this stage one of the most characteristic symptoms of the disease may be seen, peeling of the skin of the palms and soles beginning under the fingertips and toes (periungual desquamation). Joint inflammation, may also be present, usually affecting the larger weight-bearing joints in this phase. Laboratory studies reveal a high platelet count (one of the cells in the blood that helps clotting) and an increase in blood proteins that promote clotting. The sedimentation rate, a blood test that shows the overall degree of inflammation, continues to be high and anemia (fewer red blood cells than usual) is common. Widening (dilation) or bubble formation (aneurysm) in the coronary arteries can be seen by echocardiogram in this phase.
THE CONVALESCENT PHASE
Third is a convalescent phase: the child continues to recover and labs return to normal. Although the child is usually feeling better, coronary aneurysms may continue to enlarge, reaching their biggest size 4 to 6 weeks from the first day of fever.
What causes Kawasaki disease?
The cause of Kawasaki disease is unknown. Many believe it is related to an infection, for several reasons. First, Kawasaki disease is almost only seen in children; suggesting adults have developed an immunity to something that may be important in causing the disease. Second, outbreaks are seen in certain geographic regions, and more cases happen in the late winter and early spring. Lastly, children with acute Kawasaki disease have an appearance that is similar in some ways to children with other infectious diseases like scarlet fever, and some viruses. However, Kawasaki disease is not spread from person to person or "catching." No bacteria or virus has ever been proven to cause Kawasaki disease, so some experts wonder whether there might be several infections at fault.
Genes may also play a role in Kawasaki disease: 1) individuals of Japanese origin, no matter where in the world they live, are more likely to get Kawasaki disease; 2) brothers and sisters of children with Kawasaki disease are more likely than other neighborhood children to get Kawasaki disease; and 3) some children of parents who had Kawasaki disease later have come down with the illness. Some studies have found associations between Kawasaki disease and recent carpet cleaning, and living near a body of stagnant water; but cause and effect have not been established. Kawasaki disease is also seen more commonly in children from higher socioeconomic groups.
Who gets Kawasaki disease?
The first cases of Kawasaki disease in the United States were described in the early 1970s. Japanese children have the highest risk of this illness, but Kawasaki disease occurs in all races. Blacks have the second highest rate of occurrence, and white children follow. Eighty-five percent of cases occur in children under age 5 years, mostly in toddlers (1- to 2-year-olds). Infants often have atypical symptoms, without fulfilling diagnostic criteria; however, this age group (especially infant males) has the highest risk of developing severe coronary artery disease. Recent research has also shown more coronary artery aneurysms in children older than 6 years. Males are more likely to get the disease than females. We do not know exactly how many children in the United States develop Kawasaki disease each year, but estimates based upon hospital discharge summaries suggest that at least 2,000 to 3,000 cases occur annually. 0.3% of children with Kawasaki disease die; almost all deaths are related to its effects on the heart.
ACKNOWLEDGEMENT TO KAWASAKI DISEASE FOUNDATION U.S.A
