The convalescent stage begins when all clinical signs of illness have disappeared, and continues until the sedimentation rate returns to normal, usually at six to eight weeks after the onset of illness.Adult onset of Kawasaki disease is rare. The presentation differs between adults and children: in particular, it seems that adults more often have cervical lymphadenopathy, hepatitis, and arthralgia.Some children, especially young infants, have atypical presentations without the classic set of symptoms. Such presentations are associated with a higher risk of cardiac artery aneurysms. Cardiac
Heart complications are the most important aspect of Kawasaki disease, which is the leading cause of heart disease acquired in childhood in the United States and Japan. In developed nations, it appears to have replaced acute rheumatic fever as the most common cause of acquired heart disease in children. Coronary artery aneurysms occur as a sequela of the vasculitis in 20–25% of untreated children. It is first detected at a mean of 10 days of illness and the peak frequency of coronary artery dilation or aneurysms occurs within four weeks of onset. Aneurysms are classified into small (internal diameter of vessel wall <5 mm), medium (diameter ranging from 5–8 mm), and giant (diameter > 8 mm). Saccular and fusiform aneurysms usually develop between 18 and 25 days after the onset of illness.Even when treated with high-dose IVIG regimens within the first 10 days of illness, 5% of children with Kawasaki disease develop at the least transient coronary artery dilation and 1% develop giant aneurysms.
Treatment
Children with Kawasaki disease should be hospitalized and cared for by a physician who has experience with this disease. In an academic medical center, care is often shared between pediatric cardiology, pediatric rheumatology, and pediatric infectious disease specialists (although no specific infectious agent has yet been identified). To prevent damage to coronary arteries, treatment should be started immediately following the diagnosis.Intravenous immunoglobulin  (IVIG) is the standard treatment for Kawasaki disease and is administered in high doses with marked improvement usually noted within 24 hours. If the fever does not respond, an additional dose may be considered. In rare cases, a third dose may be given. IVIG is most useful within the first seven days of fever onset, to prevent coronary artery aneurysm. IVIG given within the first 10 days of the disease reduces the risk of damage to the coronary arteries in children, without serious adverse effects.Salicylate therapy, particularly aspirin, remains an important part of the treatment (though questioned by some) but salicylates alone are not as effective as IVIG. There is limited evidence to indicate whether children should continue to receive salicylate as part of their treatment. Aspirin therapy is started at high doses until the fever subsides, and then is continued at a low dose when the patient returns home, usually for two months to prevent blood clots from forming. Except for Kawasaki disease and a few other indications, aspirin is otherwise normally not recommended for children due to its association with Reye syndrome.