Epidemiology
Kawasaki disease is the second most common vasculitis in children, with the first being Henoch-Schonlein Purpura (also known as IgA vasculitis). It predominantly affects children under the age of 5, with an incidence of 4.5 per 100,000 children in the UK. It is far more prevalent in patients of Northeast Asian descent, particularly in Japan and Korea. In developed countries, Kawasaki disease is the leading cause of acquired heart disease.
Pathophysiology
The exact cause of Kawasaki disease is still unknown. However, there are some trends that suggest the involvement of infection in a genetically susceptible host. The trends that raise suspicion of an infectious aetiology include:
- Seasonal variation of the disease - it is more common in winter and spring
- Geographical distribution - it is more common in individuals of Japanese descent.
- Age of onset - as children have developing immune systems.
Despite all of this, we still have no identifiable pathogen that we can link to the development of Kawasaki disease.
This vasculitis primarily affects the medium-sized arteries of the body, particularly the coronary arteries, as well as the radial, femoral, and splenic arteries. The disease process begins with oedema and infiltration of neutrophils and mononuclear cells in these arteries. Subsequently, matrix metalloproteinases (MMPs) are released, leading to the destruction of the internal elastic lamina and tunica media layers. Luminal myofibroblastic proliferation then occurs, where fibrous tissue replaces the internal elastic lamina and tunica media. This predisposes the coronary arteries to aneurysms, scarring, and stenosis.
⚠️ Risk factors
- Japanese ancestry
- <5 years old - although it has rarely been noted in infants <3 months old.
😷 Presentation
There are phases of Kawasaki disease:
- Acute phase
- Subacute phase
- Convalescent stage
Acute phase
It lasts approximately 1-2 weeks. In this stage the child is most unwell with a fever, rash and lymphadenopathy.
Subacute phase
This is the next 2-4 weeks. In this stage, the acute symptoms settle down and in place we get arthralgia and desquamation. There is also a risk of coronary artery aneurysm formation and coronary thrombosis (due to thrombocytosis) .
Convalescent stage
This occurs over the subsequent 2-4 weeks. The symptoms begin to settle, along with the derangements in blood tests. The coronary aneurysm begins to regress but with fibrosis formation. This may lead to stenosis which can still cause ischaemia and infarction.
The child is unhappy and unwell. They are often subdued more than what is typically seen in other febrile illnesses like URTI's and UTI's.
- High-grade fever - above 39ºC and persists >5 days.
- CREAM
- Conjunctivitis - bilateral and non-exudative.
- Rash - a widespread, erythematous, maculopapular rash.
- Erythema and oedema of the hands and feet - this later progresses into desquamation of the affected skin.
- Adenopathy - cervical lymphadenopathy. It is unilateral and non-tender.
- Mucosal involvement - oral mucositis, cracked lips, strawberry tongue (red tongue with large papillae).
Investigations
⭐️ It is a clinical diagnosis.
Although the fever persists for 5 or more days, the Single Hub and Access point for paediatric Rheumatology in Europe (SHARE) recommends that a diagnosis can be reached before 5 days of fever if:
- 4 of the 5 symptoms are met (the CREAM symptoms)
- OR if there is evidence of coronary artery dilation
- OR if there is evidence of persistent inflammation with no alternative diagnosis and a clinical suspicion of KD.
💡 Children who do not meet the full diagnostic criteria, such as having a long-lasting fever with only 2 or 3 principal features, should be considered to have incomplete KD.
Some results in favour of a diagnosis of Kawasaki disease are:
- FBC - anaemia, thrombocytosis, leukocytosis
- LFT's - hyperalbuminaemia, elevated liver enzymes
- Inflammatory markers - raised ESR and CRP
- Urinalysis - raised white cell count without other UTI indicators i.e nitrites
- 🥇 Echocardiogram - coronary artery pathology identifiable
- 🥈 Angiography
🧰 Management
- 🥇 IVIG (intravenous immunoglobulins) - given if the child presents within the first 10 days of KD (or after, if inflammatory processes are still going on). A single infusion is the standard treatment. It reduces fever and chance of getting coronary artery aneurysms.
- 🥇 Aspirin - high dose aspirin must be given to all children with KD as it reduces the risk of thrombosis.
- 80-100 mg/kg/day orally, given in 4 divided doses for 24-72 hours after fever cessation, followed by low-dose 3-5 mg/kg OD for 6-8 weeks
- Regular echocardiograms for ongoing surveillance of coronary artery aneurysms.
💡 This is one of the few indications of aspirin in children, as we usually strictly avoid its use due to the risk of Reye's syndrome (rapidly progressing encephalopathy).
🚨 Complications
- ⭐️ Coronary artery aneurysm