A childhood fever of unknown cause that targets the heart's arteries
In 1967 a Japanese paediatrician, Tomisaku Kawasaki, described a puzzling illness in small children: days of stubborn fever, red eyes, a strawberry-red tongue, swollen hands. Nearly sixty years later its trigger remains unknown, yet it has become the leading cause of heart disease acquired in childhood across wealthy countries.
The illness mostly strikes children under five. It is a vasculitis, meaning medium-sized blood vessels throughout the body become inflamed. The fever usually runs above 39 degrees, shrugs off ordinary fever reducers and ignores antibiotics. Around it gather other signs: inflamed but painless eyes, cracked swollen lips, a rash on the trunk, a swollen gland in the neck, and red, puffy palms and soles that make toddlers refuse to hold things or stand. Two or three weeks in, skin often peels from the fingertips and toes, and months later grooves can appear across the nails.
Despite looking like an infection, it does not pass between people. The leading idea is that certain infections set off an exaggerated immune reaction in children who are genetically inclined to respond that way. That makes diagnosis a matter of pattern recognition, since measles, scarlet fever and juvenile arthritis can look similar. Some infants show only part of the pattern, and those incomplete cases carry a higher risk to the heart.
The real danger lies in the coronary arteries. Left alone, the inflammation weakens their walls, and balloon-like aneurysms form in about a fifth to a quarter of children, usually in the weeks after the fever fades, when the risk of sudden death peaks. Even as vessels heal, scarring can narrow them and starve heart muscle of oxygen. Heart attacks in these children look unlike adult ones, often striking during sleep, and roughly a third cause no symptoms at all.
Geography adds another riddle. Outside Japan the disease reaches between 8 and 67 of every 100,000 young children each year, but in Japan the figure climbs to 124. Boys are affected more than girls. In developed nations it appears to have overtaken rheumatic fever as the top cause of acquired heart disease in children.
Source: Kawasaki disease
