Kawasaki Disease

Kawasaki Disease (also known as mucocutaneous lymph node syndrome) is a paediatric vasculitis of unknown aetiology primarily affecting children under five years of age. This disease is characterised by an inflammatory response in medium-sized blood vessels throughout the body and is the leading cause of acquired heart disease in children in developed countries.

Signs and Symptoms

Kawasaki disease often begins with a high and persistent fever lasting more than five days and not responsive to typical antipyretic medications. The fever is usually above 39–40°C and is accompanied by extreme irritability. Bilateral conjunctival inflammation is common, typically involving the bulbar conjunctivae without suppuration or pain. Mouth symptoms include a red tongue, swollen lips with vertical cracking, and a "strawberry tongue" appearance.

Cervical lymphadenopathy occurs in 50-75% of children, often presenting as a painless or minimally painful swollen lymph node in the neck. Less common symptoms can affect various systems, including gastrointestinal (diarrhoea, abdominal pain), musculoskeletal (polyarthritis), cardiovascular (myocarditis, tachycardia), genitourinary (urethritis, nephrotic syndrome), central nervous system (aseptic meningitis, sensorineural deafness), respiratory (shortness of breath), and skin (rash, erythema at BCG vaccination site).

In the acute phase, erythema of the palms and soles with painful swelling is common. This is followed by desquamation of the fingers and toes within two to three weeks after the fever starts. A maculopapular erythematous rash, primarily on the trunk, is also observed.

Diagnosis

Diagnosis is primarily clinical, supported by laboratory and imaging findings. The classical diagnostic criteria include fever of ≥5 days and at least four of the following:

1. Bilateral nonsuppurative conjunctivitis
2. Changes in the mucous membranes (red throat, dry cracked lips, "strawberry" tongue)
3. Changes in the extremities (redness, swelling, peeling skin)
4. Polymorphous rash
5. Large cervical lymph nodes (>15 mm)

Additional diagnostic tests include complete blood count showing normocytic anaemia and thrombocytosis, elevated erythrocyte sedimentation rate and C-reactive protein, liver function tests, electrocardiogram, echocardiogram, and ultrasound or CT for gallbladder hydrops.

Differential diagnosis includes scarlet fever, toxic shock syndrome, juvenile idiopathic arthritis, and conditions mimicking Kawasaki disease like measles, adenovirus, and Stevens Johnson syndrome.

Treatment

Hospitalisation and treatment by experienced paediatricians are essential. Intravenous immunoglobulin (IVIG) is the standard treatment, administered in high doses, ideally within the first seven days of fever onset to prevent coronary artery aneurysm. Aspirin therapy is also used, starting at high doses until the fever subsides and then at low doses for up to two months to prevent blood clots. Vaccinations against varicella and influenza are recommended due to the risk of Reye syndrome.

For children who do not respond to initial IVIG therapy, corticosteroids, TNF alpha blockers, and other immunosuppressants may be considered. However, corticosteroids are generally contraindicated due to the risk of coronary artery aneurysm. Cyclophosphamide and plasma exchange have also been investigated for refractory cases.

Prognosis

Early treatment usually results in rapid recovery and significantly reduces the risk of coronary artery aneurysms. However, untreated Kawasaki disease can lead to severe complications, including myocardial infarction and sudden death. Persistent inflammation and altered lipid metabolism are long-term concerns, necessitating ongoing monitoring and potential intervention for coronary artery lesions.

Epidemiology

Kawasaki disease predominantly affects boys and people of Asian descent, particularly Japanese. The incidence rate is highest in Japan, followed by increasing rates in other countries, including the United States and the United Kingdom. It remains a significant cause of paediatric vasculitis worldwide and has replaced acute rheumatic fever as the most common cause of acquired heart disease in children in developed nations.

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Self-assessment MCQs (single best answer)

What is the leading cause of acquired heart disease in children in developed countries?

Which age group is primarily affected by Kawasaki disease?

Which of the following is NOT a common sign or symptom of Kawasaki disease?

What is the primary characteristic of the rash seen in Kawasaki disease?

Which laboratory finding is commonly associated with Kawasaki disease?

What is the first-line treatment for Kawasaki disease?

Which of the following is a potential complication of untreated Kawasaki disease?

Which diagnostic criterion is NOT part of the classical diagnosis of Kawasaki disease?

In which country is the incidence rate of Kawasaki disease the highest?

Why are vaccinations against varicella and influenza recommended for children with Kawasaki disease?