Kawasaki Disease

Definition

Kawasaki disease is an acute, self-limiting vasculitis that predominantly affects children under the age of 5. It involves inflammation of the blood vessels throughout the body, including the coronary arteries, which supply blood to the heart. Kawasaki disease is the leading cause of acquired heart disease in children in developed countries, and it requires early diagnosis and treatment to prevent long-term complications.

Aetiology

The exact cause of Kawasaki disease is unknown. It is thought to be triggered by an abnormal immune response to an infection in genetically susceptible individuals. Several factors may be involved, including:

• Infections: Viral or bacterial infections may play a role in triggering the immune response.
• Genetic predisposition: Some children may have a genetic susceptibility to Kawasaki disease, with certain ethnic groups, particularly those of East Asian descent (e.g. Japanese or Korean), being more commonly affected.
• Environmental factors: Geographic and seasonal variations suggest that environmental factors may influence the occurrence of Kawasaki disease.

Pathophysiology

Kawasaki disease primarily affects the medium-sized arteries, causing inflammation (vasculitis) of the vessel walls. The immune system mistakenly attacks the body's own blood vessels, leading to widespread inflammation. The coronary arteries, which supply blood to the heart muscle, are particularly vulnerable. If untreated, this inflammation can cause complications such as coronary artery aneurysms, which can lead to thrombosis, myocardial infarction, or sudden death.

The disease progresses through three phases:

• Acute phase: Lasting 1-2 weeks, marked by fever and acute inflammation of the blood vessels.
• Subacute phase: Lasting 2-4 weeks, characterised by peeling of the skin on the hands and feet, and the risk of coronary artery aneurysms developing.
• Convalescent phase: Lasting 6-8 weeks after the onset of symptoms, with resolution of clinical signs but potential ongoing coronary abnormalities.

Risk Factors

Risk factors for Kawasaki disease include:

• Age: Most common in children under 5 years old.
• Gender: Boys are more likely to develop Kawasaki disease than girls.
• Ethnicity: Children of East Asian descent, particularly Japanese or Korean, are at higher risk.
• Family history: Having a sibling who has had Kawasaki disease increases the risk.

Signs and Symptoms

The signs and symptoms of Kawasaki disease usually appear in phases:

Acute phase:

• Fever: High fever (typically >38.5°C) that lasts for more than 5 days and does not respond to antipyretics.
• Rash: A widespread rash, often starting on the trunk and spreading to the limbs.
• Red eyes (conjunctivitis): Bilateral non-purulent conjunctivitis (red eyes without discharge).
• Swollen lymph nodes: Typically one large lymph node in the neck.
• Swollen hands and feet: Redness and swelling of the palms and soles.
• Red, cracked lips and strawberry tongue: The tongue becomes bright red with prominent papillae, and the lips may be cracked and dry.

Subacute phase:

• Peeling skin: Desquamation (peeling) of the skin on the hands and feet, particularly around the fingertips and toes.
• Arthritis: Joint pain and swelling may occur.

Convalescent phase:

The signs gradually subside, but coronary artery complications may persist.

Investigations

There is no specific test for Kawasaki disease, but the following investigations help in diagnosis and management:

• Blood tests: Raised inflammatory markers (ESR, CRP), elevated white blood cell count, thrombocytosis (high platelet count), and anaemia.
• Echocardiogram: To assess the coronary arteries for aneurysms and cardiac function.
• Urinalysis: May show sterile pyuria (white blood cells in urine without infection).
• Electrocardiogram (ECG): To monitor heart rhythm and detect any abnormalities.

Diagnosis

Diagnosis of Kawasaki disease is clinical, based on the presence of fever lasting more than 5 days, combined with at least 4 of the following signs:

• Bilateral non-purulent conjunctivitis.
• Rash (polymorphous exanthem).
• Cervical lymphadenopathy (≥1.5 cm in diameter).
• Changes in the extremities (swelling or erythema of the palms and soles).
• Changes in the lips and oral cavity (red, cracked lips, strawberry tongue).

If fewer than 4 of these signs are present, Kawasaki disease may still be considered if there is evidence of coronary artery involvement on echocardiography.

Management

The goal of treatment is to reduce inflammation and prevent coronary artery complications. Early diagnosis and treatment within 10 days of symptom onset significantly reduce the risk of complications:

• Intravenous immunoglobulin (IVIG): The mainstay of treatment, given as a single infusion within the first 10 days of illness to reduce inflammation and the risk of coronary artery aneurysms.
• Aspirin: Initially given at high doses to reduce inflammation and fever, followed by low-dose aspirin to prevent blood clots.
• Corticosteroids: May be considered in cases resistant to IVIG or in children with a high risk of coronary complications.
• Long-term follow-up: Children with coronary artery aneurysms may require long-term monitoring and management, including additional medications like anticoagulants.

References

1. NHS (2024) Kawasaki Disease. Available at: https://www.nhs.uk/conditions/kawasaki-disease (Accessed: 26 August 2024).
2. National Institute for Health and Care Excellence (NICE) (2024) Kawasaki Disease: Diagnosis and Management. Available at: https://www.nice.org.uk/guidance/ng51 (Accessed: 26 August 2024).