Kawasaki disease (KD) is a rare but serious illness recognized as a form of vasculitis, meaning it causes inflammation in the walls of blood vessels throughout the body. It primarily affects children under the age of five and is the leading cause of acquired heart disease in this age group in developed countries. The most significant concern is the inflammation’s effect on the coronary arteries, the vessels that supply the heart muscle itself. Understanding the risk of a second episode and the long-term implications is important for parents and caregivers.
The Likelihood and Risk Factors for Recurrence
The possibility of Kawasaki disease returning is a concern, and while recurrence is uncommon, it is a recognized phenomenon. Studies indicate the recurrence rate is low, typically ranging from 1% to 4% of patients who experience an initial episode. Recurrence most frequently occurs within the first two years following the initial illness. Recurrent KD is more likely to strike children who were younger than one year old during their first episode, with infants having a recurrence rate more than double that of older children. Other risk factors include resistance to the initial treatment with Intravenous Immunoglobulin (IVIG), or a longer duration of fever before initial IVIG treatment.
Recognizing the Signs of Recurrent Kawasaki Disease
Recognizing a second episode requires vigilance because the symptoms closely mirror the first occurrence. The primary sign remains a persistent high fever lasting five days or more. Other classic features include:
- Changes in the extremities, such as swelling and redness of the hands and feet.
- A widespread rash.
- Redness in both eyes without discharge.
- Swollen lymph nodes in the neck.
- Changes in the mouth, such as cracked lips or a “strawberry tongue.”
The clinical presentation of recurrent KD can sometimes be less straightforward than the initial diagnosis. Some children may experience an “incomplete” presentation, showing only a few classic symptoms alongside the prolonged fever. Prompt re-evaluation is necessary if a child with a history of KD develops a fever, as recurrent episodes carry a risk of coronary artery damage equal to or greater than the first.
Long-Term Cardiovascular Risks and Complications
The most significant long-term concern following Kawasaki disease is damage to the coronary arteries. Inflammation can weaken artery walls, leading to coronary artery aneurysms, which are bulges in the vessel. These aneurysms pose a severe risk because they cause turbulent blood flow, increasing the chance of blood clot formation (thrombosis). Over time, the healing process within the damaged artery can cause the vessel wall to thicken and narrow, a condition known as coronary artery stenosis. Stenosis restricts blood flow to the heart muscle, potentially leading to myocardial ischemia or a heart attack.
To manage this risk, physicians use a specialized measurement called a Z-score, which compares the measured diameter of the child’s coronary artery to the expected diameter for their body size. This Z-score system provides a standardized classification for risk, ranging from simple dilation (Z-score 2.0 to < 2.5) to small, medium, and large or giant aneurysms (Z-score ≥ 10.0 or absolute diameter ≥ 8 mm). Patients with giant aneurysms are at the highest lifetime risk for complications. The long-term prognosis is directly determined by the maximum coronary artery Z-score reached during the acute illness.
Post-KD Follow-up and Monitoring Protocols
Long-term management of a patient with a history of Kawasaki disease is highly individualized and depends on the degree of coronary artery involvement, as classified by the Z-score. For children whose coronary arteries remained normal throughout the illness, follow-up is generally limited to echocardiograms at two weeks, six to eight weeks, and potentially one year after the initial diagnosis. If all these tests are normal, no further specialized cardiac follow-up may be necessary, though general cardiovascular health remains important.
Patients with any degree of coronary artery abnormality require continuous, lifelong monitoring with a pediatric cardiologist. Those with small or medium aneurysms need regular echocardiograms and sometimes stress tests to check for blockages. For patients who developed large or giant aneurysms, the monitoring is significantly more intensive, including echocardiograms every few months and the use of advanced imaging techniques like CT or MRI.
Medical management centers on preventing thrombosis within any damaged vessel segments. Low-dose aspirin is the most common antiplatelet medication used for its clot-preventing effects. It is continued for six to eight weeks in uncomplicated cases, but indefinitely for patients with persistent coronary artery aneurysms. Those with the highest risk, such as giant aneurysms, often require the addition of anticoagulants like warfarin or low-molecular-weight heparin to further reduce the risk of blood clots.