Kawasaki disease is a rare syndrome of unknown origin that affects children. It involves inflammation of the blood vessels, and it affects the arteries. It can have a serious long-term effect on the heart.

According to The Kawasaki Disease Foundation, around 80 percent of patients are under the age of 5 years. Less commonly, it affects older children and teenagers.

It does not usually affect children under 6 months, possibly because they are protected by antibodies from their mother.

In the United States, 19 children in every 100,000 are admitted to the hospital with Kawasaki disease every year.

Inflammation occurs in the walls of arteries throughout the body, including the coronary arteries, which supply blood to the heart muscle.

As it affects the lymph nodes and skin and mucous membranes inside the nose, mouth, and throat, it is also called mucocutaneous lymph node syndrome.

It is not contagious.

Signs and symptoms develop in three phases.

Acute phase, or phase 1

Symptoms appear from day 1 to 11. They emerge suddenly and are usually intense.

They include:

  • High body temperature, or fever, which continues for at least 5 days and may reach 104 degrees Fahrenheit or 40 degrees Celsius. The fever does not respond to over-the-counter (OTC) painkillers, such as ibuprofen or Tylenol (paracetamol)
  • Conjunctivitis in both eyes, where the whites of the eyes become red, and the eyes may be itchy, watery, and sore
  • Sore throat
  • Swollen, chapped, and dry lips
  • Red, swollen tongue, often with small lumps at the back, sometimes referred to as strawberry tongue
  • Swollen lymph glands and lumpiness on the neck
  • A rash on the arms, legs, and torso, and between the genitals and the anus
  • A second rash on the palms of the hands and the soles of the feet, which may be accompanied by peeling skin

Children who develop a rash may find it uncomfortable to move their legs.

Sub-acute, second phase

Symptoms appear from days 12 to 21. They are less severe, but they may persist for longer. The body temperature should return to normal.

Symptoms may include:

  • Peeling of the skin on toes and fingers
  • Vomiting
  • Diarrhea
  • Abdominal pain
  • Joint pain
  • Joint swelling
  • Jaundice
  • Lack of appetite

Complications are more likely to occur during this phase and the child may experience more pain and be moody.

Convalescent, or third phase

This phase lasts from about day 22 to day 60. Symptoms improve, and the patient gradually recovers until all signs of the disease are gone.

The main concern is that Kawasaki can affect the vessels around the heart so the patient must undergo evaluation with an echocardiogram.

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Kawasaki disease affects the mucous membranes.

Experts do not know what causes Kawasaki disease.

One possibility is that it may be an abnormal response to a common virus that most people do not react to. Symptoms resemble those of a virus or an infection, but no specific viral or bacterial cause has been identified.

Another is that it is an autoimmune disorder, where the body's immune system attacks its own good tissue as if it were a pathogen, or organism that causes disease.

The following may be considered risk factors for Kawasaki disease:

  • Age: It is more likely between the ages of 1 year and 5 years
  • Gender: Boys are more likely than girls to develop it
  • Ethnic background: People of Asian ancestry, specifically Japanese or Chinese, and Black Americans are more susceptible to Kawasaki disease
  • Genetics: If the parents had Kawasaki disease, their offspring may be more likey to have it, suggesting that it may be linked to an inherited gene
  • Environment: In the northern hemisphere, from January through March, the rate is 40 percent higher than in August through October.

Some suggest it may be a reaction to some toxins or medications, but clinical evidence is lacking.

To have a diagnosis of Kawasaki disease, there must be a fever for 5 or more days as well as four out of five main other findings:

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Conjunctivitis can be a symptom of Kawasaki disease.
  • Conjunctivitis
  • Changes in the lips or mouth
  • Enlarged lymph nodes in the neck
  • Rash on the body
  • Changes on the hands or soles of feet

Currently, no one specific test can confirm Kawasaki disease.

Since the symptoms are similar to other childhood diseases, including the measles, scarlet fever, and juvenile arthritis, some tests may be ordered to eliminate those diseases.

A physician will consider the patient's symptoms and carry out a physical examination.

Blood and other tests can check for:

  • An elevated white blood count
  • Inflammation in the joints
  • A high sedimentation rate
  • Mild anemia
  • The presence of protein or white blood cells in the urine

An echocardiogram can check for damage to the heart and coronary arteries.

Tests

Tests that may be carried out include:

  • Urine test: This can help indicate whether something else may be causing symptoms.
  • Platelet count: Platelets are cells in the blood that clump together to help stop bleeding, and in Kawasaki disease, they are usually high.
  • Erythrocyte Sedimentation Rate (ESR) test: A sample of red blood cells is placed into a test tube of liquid. If the time taken for the red blood cells to fall to the bottom is fast, this can indicate an inflammatory condition, such as Kawasaki.
  • C-reactive protein (CRP) test: A high level of C-reactive protein in the blood, produced by the liver, can indicate an inflammation.
  • Sodium test: Low sodium may be present.
  • Albumin test: There may be low levels of albumin, a protein, in the blood.

Kawasaki disease can affect the heart.

The following tests may be ordered:

  • Electrocardiogram (ECG): This device records electrical activity and heart rhythms. Electrodes are attached to the patient's skin, and impulses are recorded as waves and displayed on a screen or printed on paper.
  • Echocardiogram: An ultrasound scan that checks the pumping action of the heart. Sound waves create a video image of the patient's heart, and this helps the doctor see how well it is pumping.

Kawasaki disease is usually treated in hospital, because of the risk of complications. Prompt treatment increases the chance of a faster recovery and reduces the risk complications.

Some medications are used in treatment.

Aspirin: Kawasaki disease leads to a very high blood platelet count, and a higher risk of clots forming in the bloodstream. Aspirin helps prevent blood clots and reduces the fever, rash and joint inflammation. A high dose will normally be necessary.

The patient must be monitored for undesirable side effects. Aspirin therapy may continue for several weeks after recovery from symptoms.

Intravenous immunoglobulin (IVIG): This decreases the risk of coronary aneurysms, but how it works remains unclear.

Corticosteroids and tumor necrosis factor inhibitors: These may be used if other therapies do not work.

The patient must receive plenty of fluids, to avoid dehydration.

After initial treatment

There will be some longer term treatment.

If a coronary artery aneurysm develops, aspirin treatment will continue for longer, but if the patient develops flu or chickenpox during treatment they will have to stop taking aspirin.

Although heart problems are rare, it is crucial to monitor the heart.

If there are any indications of heart problems, the doctor may order follow-up tests, usually 6 to 8 weeks after symptoms started.

If the heart problems persist, the doctor may refer the patient to a pediatric cardiologist, a doctor specialized in diagnosing and treating childhood heart problems.

The following may be necessary:

  • Anticoagulant medications, such as warfarin, heparin, or aspirin, to prevent blood clots
  • Coronary artery angioplasty, a procedure opens up an artery that has narrowed by inflating a small balloon inside the artery
  • Alongside the angioplasty, a stent may be placed in a clogged artery to help prop it open, reducing the risk of it blocking again

In a coronary artery bypass graft, blood flow is rerouted round a diseased coronary artery by grafting a section of blood vessel from the chest, arm or leg to use as the alternate route.

The bypass goes round the blocked artery, allowing blood to pass through into the heart muscle.

Prompt treatment reduces the risk of complications, and most patients do not experience further problems.

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After recovering from Kawasaki disease, the heart should be monitored for continuing health.

Although heart problems are rare, The American Academy of Pediatrics notes that Kawasaki disease is the leading cause of acquired heart disease in infants and young children in the U.S.

The Arthritis Foundation note that up to 1 in 4 children may develop problems in their coronary arteries, even with proper treatment, and Kawasaki disease is fatal in about 1 percent of cases.

Left untreated, Kawasaki disease can cause serious complications, including an aneurysm.

If an aneurysm develops, the blood vessels leading to the heart become inflamed, causing a section of the artery wall to weaken and bulge outwards. If the aneurysm does not heal itself, a blood clot can form, which raises the risk of a heart attack or internal bleeding if the aneurysm bursts.

Other complications include:

  • Heart muscles and heart valves malfunction
  • Myocarditis, an inflammation of the myocardium, or heart muscle
  • Pericarditis, an inflammation of the pericardium, the lining around the heart
  • Heart failure or heart attack

Kawasaki disease can affect other body systems including the nervous, immune, digestive, and urinary systems.

People who have had Kawasaki disease may be advised to have an echocardiogram every 1 to 2 years, to screen for heart problems.

Patients normally recover within a few weeks, even if there are heart or other complications.