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Why early diagnosis of Kawasaki disease is vitally important

Specialist

Dr David Burgner discusses with GP Dr Anthony Harnden what GPs should be especially vigilant for

awasaki disease is the commonest cause of acquired paediatric heart disease in the industrialised world. The coronary damage varies from mild dilatation to giant coronary artery aneurysms, which often resolve to leave coronary insufficiency and ischaemic heart disease in childhood. Kawasaki disease is also emerging as an important risk factor for adult-onset ischaemic heart disease. With early and appropriate treatment, coronary artery damage can be prevented in most children.

Kawasaki disease is an inflammatory vasculitis affecting infants and young children. The disease has a predilection for the coronary arteries, damaging them in up to one-third of untreated cases, with an acute mortality of up to 4 per cent. So how do you make the diagnosis and what should GPs be especially vigilant for?

The cause is unknown, although it appears to result from an abnormally vigorous inflammatory immune response to one or more unidentified infection(s). There is no diagnostic test. The diagnosis is made clinically, on the basis of defined clinical criteria (see box).

Kawasaki disease is especially common in the under-fives but it is important to remember it may occur at any age and in any ethnic group.

Recent reports suggest there are approximately 300 cases per year in the UK, although precise estimates are difficult without enhanced surveillance. The incidence appears to be increasing worldwide.

Children with active Kawsaski disease have a persisting fever and are usually extremely miserable. This irritability may help differentiate Kawasaki disease from many self-limiting viral infections. The diagnostic criteria are: prolonged fever (five or more days), plus four or more of the five clinical criteria (see box).

However, children often present without the 'full house' of diagnostic features, as these often develop sequentially, so a high index of clinical suspicion is needed. The fever in Kawasaki disease is often marked and poorly responsive to anti-pyretics.

Other features that may occur include swelling at the site of a recent BCG vaccination, joint pain, abdominal pain, diarrhoea and dysuria. Peeling of the fingers and toes is a late sign, typically occurring in the second week of the illness.

Blood tests are rarely helpful acutely in primary care; thrombocytosis is also a late feature and is not helpful in making the acute diagnosis. Differential diagnoses include infection (especially measles, adenovirus and streptococcal infections such as scarlet fever) and rarer autoimmune diseases, such as juvenile chronic arthritis and systemic lupus erythromatosis.

Why is early recognition of Kawsaski disease important? The best available treatment is intravenous immunoglobulin and aspirin, preventing coronary artery damage in more than

90 per cent of children. Treatment is generally more effective if given early in the disease. Children with suspected Kawasaki disease should be referred urgently to their local paediatric centre, with the possibility of the diagnosis highlighted.

The consequences of a missed diagnosis for the individual child may be devastating. If the diagnosis is confirmed in hospital, serial echocardiograms are performed to identify any coronary artery abnormalities and low-dose aspirin is continued at least until a normal echocardiogram at six weeks.

Kawasaki disease is one of the few indications for aspirin in children. Continuing specialist follow-up will be required if there is coronary damage. All families should be counselled about coronary risk factors, as the long-term cardiovascular implications of Kawasaki disease, even in the absence of obvious coronary artery damage, are unknown.

There is an active parent support group for families affected by Kawasaki disease, who welcome new members and are able to provide advice and support.

Live vaccines (such as MMR) are ineffective for at least three months after intravenous immunoglobulin and their administration should be delayed.

While most GPs will rarely encounter a child with Kawasaki disease it is essential that the diagnosis is considered in a miserable young child with prolonged fever. Careful examination for associated clinical features is important. Early referral and treatment may prevent life-threatening complications.

Early referral and treatment may prevent

life-threatening complications~

Kawasaki disease diagnostic criteria

Fever of five or more days plus four of the following five criteria

 · Changes in the mucous membranes: red, cracked lips, strawberry tongue and red pharynx (tonsillar exudates absent).

 · Changes in peripheral extremities: swollen hands and feet, palmar erythema, peeling of fingers and toes and sometimes groin area (usually occurs in the second week)

 · Bilateral non-purulent conjunctivitis, often with limbic sparing.

 · Polymorphous rash: often truncal distribution, may have many features and resemble other conditions (petechiae not present).

 · Lymphadenopathy: usually cervical and unilateral, often more than 1.5cm in diameter, often non-tender, present in approximately

80 per cent of cases.

Other features may include irritability and extreme misery (very common), joint pain, abdominal pain and dysuria. Note that features may develop sequentially and may not all be obvious at presentation.

The diagnosis should be considered in any young child with a prolonged fever as early treatment dramatically reduces the incidence of coronary artery lesions.

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