What is Kawasaki disease?
Kawasaki disease is an acute febrile illness with inflammation of small- and medium-sized blood vessels throughout the body, in particular, the coronary arteries (blood vessels around the heart).
Kawasaki disease was previously known as mucocutaneous lymph node syndrome. It was first described in Japan in 1967 by Dr Tomisaku Kawasaki, a paediatrician.
Without treatment Kawasaki disease is usually self-limiting illness and resolves spontaneously within 4-8 weeks. However, about 20% of untreated cases develop coronary artery damage and approximately 2% of patients will die, most commonly from a heart attack. This outlook is improved significantly with appropriate treatment.
Who gets Kawasaki disease?
Eighty percent of cases occur in children younger than 5 years of age with a peak incidence between 1 to 2 years. The disease is very uncommon in those over 14 years old and in adults. Overall it occurs more commonly in boys than girls.
Although cases of Kawasaki disease have been reported in children of all ethnic origins, the highest incidence is in children of Asian descent especially Japanese. There are 5000-6000 cases each year in Japan.
What causes Kawasaki disease?
The cause of Kawasaki disease is unknown.
What are the signs and symptoms of Kawasaki disease?
There are several clinically apparent stages of Kawasaki disease.
Typically a child with Kawasaki disease has a high swinging fever (beyond 39C), associated with a number of other features. The 5 cardinal signs of Kawasaki disease are:
- Rash – the rash of Kawasaki disease may be morbilliform (measles-like), maculopapular (red patches and bumps), erythematous (red skin) or target-like and may be persistent over days or evanescent. Skin peeling may occur in the convalescent stage of the illness.
- Oral signs – the typical changes include redness within the mouth or on the pharynx, strawberry tongue, and red or cracked lips.
- Eye signs – redness of the bulbar conjunctivae (whites of the eyes) without exudate or stickiness.
- Peripheral limb signs – including firm swelling of the hands and feet, sometimes including the fingers and toes, with redness of the palms and soles. Periungual desquamation (peeling of skin around the fingernails) may occur during the convalescent stage of the illness.
- Lymphadenopathy – swollen lymph glands can occur, often on one side of the neck. One lymph gland of at least 1.5cm in length is considered diagnostically enlarged.
Not all of the cardinal signs may be present in any one child with Kawasaki disease and not all features may be present at the same time. Some features may appear and disappear before others arise.
Children with Kawasaki disease are often unusually irritable, out of proportion to the other signs exhibited. They may also have a range of other non-specific symptoms and signs including abdominal pain, diarrhoea, dysuria (pain passing urine), joint pain or arthritis, signs of meningitis or heart failure.
How is Kawasaki disease diagnosed?
There is no specific lab test that establishes the diagnosis of Kawasaki disease. definitively. The diagnosis is considered established when the following diagnostic criteria are met:
- Fever for at least 5 days AND
- At least 4 of the 5 cardinal signs listed above AND
- The absence of any other illness to account for the signs and symptoms.
Atypical or incomplete cases of Kawasaki disease, in which patients have fever and fewer than 4 of the 5 cardinal features, are now diagnosed more commonly. In these children, the diagnosis may be supported by findings on an early 2-dimensional echocardiography (heart ultrasound) to detect coronary artery disease or other signs of acute heart disease.
Illnesses that might present with some of the features of Kawasaki disease include scarlet fever, staphylococcal scalded skin syndrome, measles and other viral exanthems (viral rashes), systemic onset juvenile arthritis (juvenile rheumatoid arthritis or Stills disease) and drug reactions (morbilliform eruption, drug hypersensitivity syndrome and Stevens Johnson syndrome / toxic epidermal necrolysis)
What is the treatment of Kawasaki disease?
Usually children are treated with antipyretic and analgesic medication (eg paracetamol / acetominophen) until the 5th day of fever is reached. Once the diagnosis of Kawasaki disease is made a single large dose of intravenous immunoglobulin (IVIG), which is purified antibodies collected from many blood donations, is given. IVIG is most effective when given between the 5th and 10th days of illness. Low dose oral aspirin is also usually commenced at this time.
IVIG greatly reduces the risk of coronary artery disease and low dose aspirin reduces the risk of clotting within the coronary artery should coronary artery disease develop. Once children are treated they generally improve rapidly; most of the acute symptoms and signs resolve within 24 to 48 hours, and the fever abates. If the signs and symptoms fail to resolve or recur within days then a 2nd dose of IVIG is given.
What are the complications of Kawasaki disease?
The main complications of Kawasaki disease are the development of dilatation and/or narrowing of one or more coronary artery. These can lead to angina, myocardial infarction or sudden death. When children are treated with IVIG up to 10 days into the illness and respond quickly, the risk of subsequent coronary artery abnormality is reduced to 2-4% and most of these have mild abnormalities many of which resolve.
Follow-up echocardiography is performed on all children with Kawasaki disease at about 6 to 8 weeks to look for coronary artery abnormalities and to check the heart is otherwise normal. If coronary artery abnormalities are demonstrated then ongoing anticoagulation treatment, such as daily aspirin, will be needed and further heart imaging will be required.
What other information do parents of children treated for Kawasaki disease need to know?
- Kawasaki disease cannot be passed on to other family members.
- There is a 2% risk of recurrence of Kawasaki disease within a period of several years.
- IVIG affects the efficacy of live virus vaccines, i.e. MMR (measles, mumps, rubella) and varicella (chickenpox) vaccines, and these should be delayed for 11 months after the last dose of IVIG is given or repeated after 11 months if given earlier.
- There is evidence that children and young people who have echocardiographic evidence of coronary artery aneurysm are more likely to develop coronary artery disease in adulthood than the general population and at an earlier age. Those with significant coronary artery disease should be followed long term by a cardiologist. Regular health examinations and cardiovascular risk assessments for these children throughout adulthood is advised.