KAWASAKI DISEASE
Introduction to Kawasaki Disease
Kawasaki disease, previously known as “mucocutaneous lymph node syndrome” and “infantile polyarteritis nodosa”, is the inflammation of medium-sized blood vessels called arteries. It commonly affects the vessels which supply oxygen-rich blood to the muscles of the heart, called the coronary arteries. It also has widespread or systemic effects on the body, the most prominent of which is persistent fever.
According to the American Academy of Pediatrics, Kawasaki disease (KD) is the most common cause of acquired heart disease in young children in America. Despite being common, it is not infectious or contagious.
Causes of KD
Up until now, there has been no established or proven cause of Kawasaki disease. Some experts have considered that certain infections may trigger KD in children. Another likely cause is genetic; some studies have shown that children of Asian ethnicity are at higher risk of developing this condition. Others contend that symptoms of KD may be an autoimmune disease, a condition wherein the body has a dysregulated or abnormal immune response that affects its own cells and body tissues.
Statistics on KD
Kawasaki disease is usually acquired during childhood. This disorder is more common in males and children with Asian and Pacific Islander ancestry. Those with Hispanic ancestry also have a slightly higher risk. Rates of admission are higher among children less than 5 years old.
Children of young age, who are male, with persistent fever, low platelet count, low serum albumin levels and low sodium levels, high brain natriuretic peptide (BNP) and high C-reactive protein levels may have more serious signs and symptoms and a complicated outcome.
What happens in KD?
In Kawasaki disease, medium-sized arteries become inflamed. The most commonly affected arteries are the coronary arteries, which supply blood directly to the heart as it is being pumped out of the heart chambers.
The changes in blood vessels encompass various phases. The first phase lasts for around two weeks, causing changes in the cells lining blood vessels. Some of these vessels may develop weak walls, dilate, and form saccular aneurysms. During the second phase, inflammation of these blood vessels continues, which may lead to a fusiform type of dilation. This can last for several weeks to months. In the last phase, affected blood vessels may form cells called myofibroblasts, causing these vessels to narrow. In some cases, blood clots may form, which can block blood flow.
Signs and Symptoms
The main clinical manifestation of KD is high-grade fever of at least 38.3C, lasting for at least 5 days, and is persistent despite giving medications for fever (called antipyretics).
There are five main clinical criteria that accompany fever. At least four are needed to diagnose a child with the classic form of Kawasaki Disease. These include:
- red eye (on both eyes) without discharge or pus
- changes in the mouth or throat (usually becoming red and inflamed), with a swollen tongue and cracked lips
- swollen hands or feet
- rashes
- swollen lymph node/s of at least 1.5 cm (found on one side of the neck), painful on its own or when touched
Among these main criteria, a red, swollen tongue is the most common symptom. This is also known as “strawberry tongue”. Additional symptoms are persistent irritability (fussiness in infants and young children), peeling skin on the fingers and toes, and even arthritis.
Some patients may experience symptoms of other infections during the first few days of KD. Around two-thirds may have abdominal pain, diarrhea or vomiting, while one-third may have cough or colds.
Additional cardiac symptoms can appear in potentially severe cases. These include inflammation of the heart (myocarditis, pericarditis), abnormalities of the coronary arteries and rupture of aneurysms.
In general, patients with Kawasaki disease undergo three clinical phases. The first one, referred to as the acute febrile phase, takes 1-2 weeks long and presents mainly with fever, principal criteria, and symptoms of any other concurrent infections. The second phase, also called the subacute phase, is characterized by increasing white blood cell count, peeling of the skin, and possible development of coronary artery aneurysms. As such, this phase is the most critical, with severe cases possibly leading to death. This phase lasts for around 3 weeks. The convalescent phase is the third and longest phase, lasting for 1-2 months. Its length is based on the inflammatory marker called the serum ESR level. This phase lasts until ESR levels normalize.
Diagnosis
Unfortunately, there is no established diagnostic test for Kawasaki disease. However, a proper rundown of the patient’s signs and symptoms, as well as certain laboratory tests, can help provide a diagnosis. The following laboratories may be requested: complete blood count, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), urinalysis, liver function tests, serum bilirubin, and 2D echocardiography.
Diagnosis of Kawasaki disease depends on the criteria: in classic KD, children experience fever for at least 4 days, with at least 4 of the 5 principal criteria. If a child exhibits less than 4 of the principal criteria, they are suspected to have atypical or incomplete KD. Additional laboratory tests should be done to assist in the diagnosis, because atypical cases have a higher risk of developing aneurysms, a serious complication.
Because newborns do not have the typical signs and symptoms of a child with Kawasaki disease, it is prudent to request for a 2D echocardiogram for children who are less than 6 months, with fever lasting for at least a week that has no plausible explanation.
Because Kawasaki disease can affect multiple organ systems and may have an accompanying infection, an affected individual may need to be referred to specialists in cardiology, rheumatology, and infectious disease.
Treatment
During the acute phase, KD may be treated with immune globulin (termed IVIG) and aspirin. IVIG should be started within 10 days of the onset of symptoms. In some cases, corticosteroids may also be given.
Complications
A few cases end up with persistent symptoms despite immune globulin therapy. These children are diagnosed with IVIG-resistant Kawasaki disease, characterized by the presence of fever 36 hours after IVIG therapy. There is a likelihood of developing dilatation of the coronary arteries in IVIG-resistant KD. Rare complications in children with IVIG-resistant KD and aneurysms are decreased blood flow to the heart and heart attacks. To prevent this, medications that decrease the formation of blood clots are also given.
Follow-up and Management
Even after hospital admission and discharge, aspirin may need to be continued for up to 2 months after the diagnosis.
Long term follow-up may be needed for patients, especially those who have developed complications or were diagnosed with IVIG-resistant KD. Doctors may request routine echocardiography, imaging studies such as CT scans or MRI, lipid monitoring, and cardiovascular risk assessment, on a case-to-case basis. Affected children should be mindful of proper physical activity and a healthy diet, avoiding exposure to tobacco smoke.
Children who were given IVIG during treatment may need to delay their measles-mumps-rubella and chickenpox vaccinations for around 11 months.
If a child develops narrowing (stenosis) of their coronary arteries, special procedures may be done to manage this condition. If aspirin is prescribed as a long-term medication, a yearly influenza vaccine is recommended.
Summary
Kawasaki disease is a systemic inflammatory condition that is not easily diagnosed and can mimic symptoms of other diseases or infections. Once identified, prompt treatment should be done in order to prevent long-term complications. Most children who receive proper treatment may still need long-term follow-up and monitoring but are more likely to have a good prognosis and quality of life.
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References:
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Kliegman, R.M. et al. (2020). Chapter 191 Kawasaki Disease. Nelson Textbook of Pediatrics 21st edition. Elsevier.
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Kawasaki Disease in Infants & Young Children (2020). Section on Cardiology ＆ Cardiac Surgery, American Academy of Pediatrics. Taken from: https://www.healthychildren.org/English/health-issues/conditions/heart/Pages/Kawasaki-Disease.aspx
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