Interleukin-2 fingers Kawasaki's syndrome.

Interleukin-2 fingers Kawasaki's syndrome

Scientists have developed a rapid test for Kawasaki's syndrome, an inflammatory disorder afflicting more than 3,000 U.S. children annually. The test may help pediatricians diagnose and treat children with Kawasaki's within the first week of illness. Standard diagnosis takes much longer, and by the time the disease is recognized, children may already have suffered heart damage, say the researchers who created the test at the Baylor College of Medicine in Houston.

"An elevated level of serum interleukin-2 receptor is a sensitive screening test in Kawasaki's syndrome. One hundred percent of patients in the first week of illness had significantly elevated levels," Karyl S. Barron told scientists this week at the American Heart Association meeting in Washington, D.C.

The Baylor team identified 82 children with Kawasaki's and found high levels of interleukin-2 receptor when they looked at the children's blood serum. During the first week of illness, these patients had receptor levels six times higher than a group of healthy controls. Interleukin-2 helps marshal the body's defense system by triggering white blood cells to attack an invading organism. To do its job, interleukin-2 has to interact with a receptor located on the white blood cell. In patients with Kawasaki's, high numbers of these receptors float freely in the blood, where they bind with interleukin-2, disrupting the immune system.

The relatively rare disorder was named after the Japanese pediatrician who identified it in 1967. Symptoms include a bright red rash, red lips and tongue, swollen hands and feet, a fever and in some cases heart damage. The disorder can be difficult to diagnose because it is often mistaken for measles. It seems much more prevalent in Japan, but public health authorities believe the disease is underdiagnosed in the United States.

The cause of the disease remains unknown, but some scientists believe it is triggered by a retrovirus similar to that causing AIDS (SN: 10/17/87, p.246). "We now hypothesize that the pathologic release of interleukin-2 receptor into the blood may explain many of the immune abnormalities seen in Kawasaki's syndrome," Barron says.

The research team found even higher levels of the receptor in Kawasaki children who later went on to develop coronary artery aneurysm, a weakening of the vessel wall. The test may be used to identify children at risk of aneurysm, enabling physicians to begin early treatment with aspirin and gamma globulin, a protein the body uses to fight infection. Right now, physicians often give aspirin/gamma globulin therapy to all Kawasaki patients even though only 20 percent of them go on to develop an aneurysm if untreated. Those who get an aneurysm run a higher risk of having a fatal heart attack, because the healed aneurysm can leave scar tissue blocking the coronary artery.

In a separate presentation at the same meeting, Barron reported that aspirin and gamma globulin treatment given to Kawasaki patients within seven days of fever onset helps prevent aneurysm formation. The efficacy of such treatment has been reported before, but Barron's study shows that a smaller dose of the expensive gamma globulin acts as effectively as larger amounts.