Kawasaki disease

Kawasaki disease is a small to medium vessel vasculitis predominantly affecting young children. It can affect any organ but there is a predilection for the coronary vessels.

Epidemiology

Japan has the highest incidence in the world, with an annual incidence of 3 per 1000 children under the age of four years ¹⁰. Worldwide, it is the most common vasculitis in children ⁹. It is slightly more common in males with a M:F ratio of 1.4:1 ¹⁰.

It is more common in siblings; ~3% of siblings will be diagnosed with Kawasaki. This equates to a ten-fold increased risk in a sibling. It is also more likely in children of affected parents, although no genetic link has been identified ¹⁰.

In the United States, it is most commonly seen in children of Asian ethnicity, in particular, Japanese, but less commonly in the Black population and least commonly in the White population.

Since April 2020, rare cases of a Kawasaki-like disorder have been reported in critically-ill children who are COVID-19 positive. A true causative association between SARS-CoV-2, the cause of COVID-19, and Kawasaki disease has not been established as yet ^14,15.

Diagnosis

Diagnostic criteria

Classic Kawasaki disease is diagnosed in the presence of fever for at least 5 days and at least 4 of the following:

• erythema and cracking of lips, strawberry tongue, or erythema of oral and pharyngeal mucosa

• bilateral bulbar conjunctival injection without exudate

• rash: maculopapular, diffuse erythroderma, or erythema multiforme–like

• erythema and oedema of the hands and feet in the acute phase

• cervical lymphadenopathy (≥ 1.5 cm in diameter), usually unilateral

Clinical presentation

Persistent fever is the commonest way with which most children present. The specific signs and symptoms vary with the stage of the disease:

Acute stage

• fever that is refractory to antibiotics

• general malaise and irritability

• non-exudative conjunctivitis (90%)

• anterior uveitis (70%)

• perianal erythema (70%)

• lymphadenitis (75%)

• strawberry tongue

Subacute stage

• desquamation of the digits

• thrombocytosis

• coronary artery aneurysms

• highest risk of death

Convalescent stage

• clinical symptoms and signs recede

Chronic stage

• persistence of any cardiac complications into adulthood

Pathology

An autoimmune aetiology has been postulated. It is generally self-limiting but acute fatalities are thought to occur in ~1% of cases. The most concerning morbidity is due to coronary involvement where it can manifest as myocarditis with coronary arterial aneurysm formation ^1,2,4.

Radiographic features

Plain radiograph

Chest radiographs can be normal. Abnormal findings are non-specific and include a reticulogranular pattern, peribronchial cuffing, pleural effusion, atelectasis and/or air trapping ¹.

Rarely, a few years after resolution of the initial episode, the patient may present with calcified coronary artery aneurysms visible on the chest x-ray ⁸. Although rare, this is an Aunt Minnie presentation of Kawasaki disease sequelae in older patients.

Angiography (coronary/CT/MRI)

May show small coronary arterial ectasias, aneurysms or stenoses. Angiography is the most sensitive and specific for vascular assessment ⁴.

Coronary artery aneurysms can be classified as ¹¹:

• small: <5 mm

• medium: 5-8 mm

• large: >8 mm

Coronary stenosis is more common in the left coronary artery while intracoronary thrombus is more frequently observed in the right coronary artery ¹¹.

MRI is also useful in assessing myocardial perfusion, wall thinning, and aneurysms.

Echocardiography

Transthoracic echocardiography is especially useful in the approach to patients who fall short of full clinical criteria (incomplete Kawasaki disease), as the presence of the following is diagnostic ¹²:

• coronary artery dilation

  • dilation which exceeds the mean coronary artery diameters by 2.5 standard deviations is classified as aneurysmal

• left ventricular dysfunction

  • inflammation of the myocardium may produce systolic or diastolic dysfunction

• mitral regurgitation

  • manifestation of endocardial inflammation

• pericardial effusion

History and etymology

It is named after the Japanese paediatrician Tomisaku Kawasaki (1925-2020) ^9,16 who saw his first case in 1961 and initially described it in a case series of 50 children in 1967 ^7,9.