Kawasaki’s disease – Diagnostics – Overview of Information and Clinical Research

Kawasaki disease can be challenging to identify because it shares symptoms with many other childhood illnesses, and no single test can confirm it. Doctors rely on a careful combination of physical examination, tracking the appearance of specific symptoms over time, and using various tests to rule out other conditions and check for heart complications.

Introduction: Who Should Undergo Diagnostics

Parents should seek medical evaluation urgently when their child has a high fever that persists for several days alongside other unusual symptoms. If your child has a fever lasting more than four days, especially if it climbs above 102.2 degrees Fahrenheit and is accompanied by a rash, red eyes, swollen hands or feet, or changes in the mouth and lips, it’s important to contact a healthcare provider immediately. Early recognition can make a significant difference in preventing serious complications^[1].

Kawasaki disease most commonly affects children under the age of five, with the majority of cases occurring in children under two years old. However, the disease can also appear in older children and, rarely, in adults. Boys are affected more frequently than girls, with a ratio of approximately 1.5 to 1. Children of Asian or Pacific Islander descent face a higher risk, though Kawasaki disease can occur in children of any ethnic background^[2]^[3].

Because infants younger than six months and adolescents often present with fewer or less obvious symptoms, these age groups are at particularly high risk of delayed diagnosis and subsequent heart complications. If an infant or adolescent has a prolonged fever without a clear cause, or if they appear unusually irritable and unwell, healthcare providers should consider the possibility of Kawasaki disease even when the full set of typical symptoms is not present^[8]^[12].

⚠️ Important

Kawasaki disease cannot be prevented, and it does not spread from person to person. The exact cause remains unknown, though researchers suspect it may involve an infectious trigger combined with genetic susceptibility. If your child has a fever for five days or more with any of the characteristic symptoms, do not wait—seek medical attention right away.

Diagnostic Methods

Clinical Diagnosis Based on Symptoms

Kawasaki disease is primarily a clinical diagnosis, meaning that doctors identify it by observing a specific pattern of symptoms rather than relying on a single laboratory test. There is no blood test, imaging scan, or other procedure that can definitively confirm the disease on its own. Instead, healthcare providers must carefully evaluate the child’s symptoms and rule out other illnesses that cause similar problems^[9]^[12].

According to established guidelines, classic or typical Kawasaki disease is diagnosed when a child has a fever lasting five or more days along with at least four of the following five features: a rash on the body, swelling and redness in the hands and feet, redness in both eyes without discharge (known as bilateral conjunctival injection), changes in the mouth such as red cracked lips or a swollen red tongue (often called “strawberry tongue”), and swollen lymph nodes in the neck, especially on one side^[1]^[3]^[14].

These symptoms do not always appear at the same time. They may develop gradually over several days, which can make diagnosis more difficult. For example, a child might have a fever and rash on the first day, develop red eyes on the third day, and show swollen hands and feet by the fifth day. Parents should inform the doctor about any symptoms that may have already resolved by the time of the medical visit^[1].

Incomplete or Atypical Kawasaki Disease

Not all children present with the full picture. Some may have what is called incomplete or atypical Kawasaki disease. This occurs when a child has a fever lasting five or more days but displays only two or three of the characteristic symptoms. Infants under one year old and adolescants are more likely to have this incomplete presentation, which puts them at greater risk for heart complications because the diagnosis may be delayed^[8]^[16].

When incomplete Kawasaki disease is suspected, doctors rely more heavily on laboratory tests and imaging to support the diagnosis. If a child has prolonged fever with fewer than four typical features, but laboratory tests show signs of inflammation and heart imaging reveals abnormalities in the coronary arteries, the diagnosis of Kawasaki disease can still be made^[13]^[16].

Ruling Out Other Conditions

Because many common childhood illnesses can cause fever, rash, and other overlapping symptoms, doctors must carefully exclude other diagnoses before confirming Kawasaki disease. Conditions such as scarlet fever, measles, toxic shock syndrome, juvenile rheumatoid arthritis, and certain tick-borne illnesses can mimic the appearance of Kawasaki disease. Viral infections are also frequently considered, as they can produce similar symptoms. Ruling out these other conditions is a critical step in the diagnostic process^[9]^[12].

Laboratory Tests

Although no single blood test can confirm Kawasaki disease, laboratory tests play an important supporting role in diagnosis. Blood tests are used to detect signs of inflammation and to rule out other diseases. Doctors typically look for an elevated white blood cell count, which suggests the body is fighting an infection or inflammation. Blood tests may also reveal anemia (a low red blood cell count) and markers of inflammation such as an elevated erythrocyte sedimentation rate (ESR) or C-reactive protein (CRP)^[9]^[12].

Urine tests may also be performed to help rule out a urinary tract infection or other causes of fever. In some children, urine may show signs of mild inflammation or abnormal cells, but these findings are not specific to Kawasaki disease. The results of these laboratory tests help doctors build a complete picture and make a confident diagnosis^[12].

Heart Imaging: Echocardiography

One of the most serious concerns with Kawasaki disease is its potential to damage the coronary arteries, which supply blood to the heart muscle. For this reason, as soon as Kawasaki disease is suspected, doctors will order an echocardiogram, which is an ultrasound of the heart. This test uses sound waves to create real-time images of the heart’s chambers, valves, and blood vessels. It is painless, does not involve radiation, and is safe for children of all ages^[9]^[12].

The echocardiogram allows doctors to look for signs of coronary artery aneurysms, which are areas where the walls of the arteries become weakened and bulge outward. These aneurysms can develop in up to 25 percent of children with untreated Kawasaki disease, but early treatment significantly reduces this risk. The echocardiogram may be repeated during treatment and after recovery to monitor the heart and ensure that any abnormalities are detected early^[8]^[12].

Electrocardiogram (ECG or EKG)

An electrocardiogram, also called an ECG or EKG, is another test that may be performed to assess the heart. This test measures the electrical activity of the heart and can detect irregular heart rhythms or other abnormalities. It is a quick and painless test that involves placing small sticky patches, called electrodes, on the child’s chest and sometimes on the arms or legs. The electrodes are connected to a machine that records the heart’s electrical signals^[9].

Although the ECG does not directly show damage to the coronary arteries, it can reveal signs of heart strain or inflammation. In combination with the echocardiogram and other tests, the ECG helps doctors evaluate the overall health of the heart and plan appropriate treatment^[9].

⚠️ Important

Even if the initial echocardiogram and ECG are normal, treatment for Kawasaki disease should still be started based on clinical symptoms and laboratory findings. Heart abnormalities can develop later, so ongoing monitoring is essential even after symptoms improve.

Diagnostics for Clinical Trial Qualification

For patients who are being considered for enrollment in clinical trials studying Kawasaki disease, additional diagnostic criteria and tests may be required. Clinical trials aim to evaluate new treatments or better understand the disease, so they often have strict eligibility requirements to ensure that participants truly have Kawasaki disease and meet other specific conditions^[15].

Typically, clinical trials will require that patients meet the standard diagnostic criteria for Kawasaki disease, meaning they have the characteristic fever lasting five or more days and the required number of clinical features. In some cases, patients with incomplete Kawasaki disease may also be eligible, particularly if they have laboratory evidence of inflammation and heart imaging that shows coronary artery involvement^[13]^[16].

Blood tests are a key part of trial screening. These may include tests for white blood cell count, markers of inflammation such as ESR and CRP, and other indicators of the body’s immune response. Some trials may also require genetic testing or additional imaging studies to assess the severity of the disease or to monitor the effects of experimental treatments^[14]^[15].

Echocardiography is usually a standard requirement for clinical trial enrollment. Because the primary goal of many Kawasaki disease trials is to prevent or treat coronary artery damage, researchers need a clear baseline assessment of the heart’s condition. An echocardiogram performed before treatment begins provides this baseline, and follow-up echocardiograms are often conducted at regular intervals throughout the study to measure the treatment’s effectiveness^[12].

Patients or their families should discuss with their healthcare provider whether participation in a clinical trial is appropriate. Clinical trials can offer access to new therapies and contribute to advancing medical knowledge, but they also involve additional tests and monitoring. Understanding the diagnostic requirements and the potential benefits and risks of participation is an important part of making an informed decision^[15].

Prognosis and Survival Rate

Prognosis

The outlook for children with Kawasaki disease is generally very good, especially when the disease is diagnosed early and treatment is started promptly. With appropriate treatment, most children recover fully within about six to eight weeks and experience no long-term health problems. Early treatment with intravenous immunoglobulin and aspirin significantly reduces the risk of developing serious complications, particularly damage to the coronary arteries^[3]^[5]^[11].

The most important factor affecting prognosis is whether the child develops coronary artery aneurysms. Without treatment, approximately one in four children with Kawasaki disease will develop these abnormalities in the blood vessels that supply the heart. However, when treatment is given early—ideally within the first ten days of illness—the risk of coronary artery damage drops significantly. Children who do develop aneurysms may require lifelong monitoring and additional treatment to prevent heart complications such as blood clots, heart attacks, or heart failure^[2]^[8]^[18].

Infants under one year of age and children who experience a delay in diagnosis are at higher risk for poor outcomes. These children may be more likely to develop coronary artery problems and may face a longer recovery period. Even children who do not develop visible coronary artery changes on imaging may face a slightly increased risk of cardiovascular disease later in life, although this risk is not fully understood. For this reason, all patients who have had Kawasaki disease should have at least periodic cardiovascular health assessments as they grow older^[14]^[17].

Survival Rate

The survival rate for children with Kawasaki disease is excellent. With modern treatment, the vast majority of children recover completely. Death from Kawasaki disease is rare, occurring in approximately two to three percent of cases, and is almost always due to severe heart complications such as coronary artery rupture, heart attack, or heart failure. These serious outcomes are much less likely when treatment is started early and when children receive appropriate long-term follow-up care^[5]^[11].

Children with persistent coronary artery aneurysms require more intensive monitoring and may need long-term medications to prevent blood clots. In severe cases, surgical procedures such as coronary artery bypass surgery may be necessary. Despite these challenges, many children with coronary artery involvement still lead active, healthy lives with proper medical management and regular follow-up with a pediatric cardiologist^[2]^[18].

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