Kawasaki disease

Kawasaki disease is acute inflammation of the walls of the small and medium arteries, and it starts in childhood, most often under the age of five. From the outside it looks like a severe infection: high fever, a rash, red eyes, cracked lips. What matters, though, is happening not in the skin but in the vessels that feed the heart, and that is why the whole story turns on speed: treatment started in time takes away almost all the threat to the heart, while days lost keep it.

How it begins

The first and most constant sign is a high temperature. It persists day after day, comes down poorly and only briefly with antipyretics, and does not respond to antibiotics if any have been started on the assumption that this is tonsillitis. The child is also irritable and inconsolable to a degree well beyond an ordinary infection, which is obvious both to parents and to an experienced paediatrician. Five days of fever is the point at which Kawasaki disease has to be taken seriously.

Five main signs join the fever in varying combinations, and not necessarily all at once:

• redness of the whites of both eyes with no pus and no stuck-together lids — the eyes are red rather than discharging as in conjunctivitis;
• bright red, dry, cracked and sometimes bleeding lips, diffuse redness of the mouth and throat, and a raspberry-coloured strawberry tongue with prominent papillae;
• a rash on the trunk and around the groin, extremely variable in appearance, from small spots to large merging patches; blisters do not occur in Kawasaki disease;
• swelling and firm redness of the palms and soles: the hands and feet look puffy, the child complains of pain on weight-bearing and may refuse to walk or crawl;
• an enlarged neck gland, usually a single one on one side, large and firm.

There is one more sign that is easily missed: redness and swelling at the site of the BCG scar, if the vaccine was given. It is a fairly characteristic finding in Kawasaki disease and worth showing to a doctor.

How the illness unfolds

The illness runs in three stretches, and knowing the order helps: much of what alarms parents in the second and third week is expected and does not mean things are getting worse.

The first week or two. The noisiest period: high fever, all the signs described above, extreme irritability. This is precisely the stretch in which treatment needs to fall.

Weeks two to four. The fever settles but the child remains listless. Peeling of the skin appears, starting at the edges of the fingernails and toenails and spreading to the palms and soles — a late sign, of no further use for diagnosis but very recognisable. Joint pain and swelling, abdominal pain, vomiting, diarrhoea and yellowing of the skin may be added. The platelet count rises sharply at this stage. The risk of heart complications is highest here.

From weeks four to six. The signs gradually withdraw and strength returns. The child tires easily for several more weeks, and sometimes transverse ridges show up on the nails later on — a mark left by the illness that simply grows out.

When it cannot wait

The rule is simple: a child whose fever has lasted five days or more must be seen by a doctor the same day, and if any one of the signs described has joined the fever, sooner than five days rather than later. In the first year of life the illness more often runs without the full picture and damages the vessels more often, so a prolonged unexplained fever in a baby means being seen straight away.

An ambulance (across Europe the single number is 112) is for something else — a child whose condition is changing fast:

• the child is drowsy and hard to rouse, does not respond as usual or, conversely, cries without stopping;
• fast, laboured breathing with drawing-in of the chest, grey or mottled skin, bluish lips, cold hands and feet;
• the rash does not fade when pressed with the side of a glass;
• the child refuses to drink, is passing noticeably less urine and cries without tears;
• fits;
• chest pain, a faint or sudden pallor with cold sweat — especially in a child who has already had Kawasaki disease with damage to the heart vessels.

In every other situation an ambulance is not the answer: sorting out a fever that has dragged on is not what it does. What is needed is a doctor examining the child — today, though, not in a week.

What else it can look like

There is no specific test for Kawasaki disease, so a doctor looks for its signs and rules out lookalikes at the same time. The resemblance comes from scarlet fever, measles, adenovirus and enterovirus infections, glandular fever, toxin-mediated staphylococcal and streptococcal skin conditions, toxic shock syndrome, drug allergy up to its severe forms, and the systemic form of juvenile arthritis. Some of these are treated in an entirely different way, so haste must not do away with proper assessment.

Multisystem inflammatory syndrome in children deserves a separate mention: it develops some weeks after a coronavirus infection. It looks a great deal like Kawasaki disease but affects older children and teenagers more often, and more often causes abdominal pain, diarrhoea and a drop in blood pressure. Telling them apart is a job for hospital; what matters for parents is that the list of reasons to see a doctor straight away is the same either way.

How the diagnosis is made

The diagnosis is put together from the examination, the length of the fever and the number of main signs. Tests do not confirm it directly but support it: the blood shows high inflammatory markers, a raised white cell count, low haemoglobin, often low albumin and sodium, sometimes raised liver enzymes, and from the second week the platelets climb noticeably. Urine often contains white cells while no bacteria grow on culture. A lumbar puncture is sometimes done to rule out meningitis.

The key investigation is an ultrasound scan of the heart, the echocardiogram. It is done as soon as the disease is suspected and then repeated on a schedule set by the doctor, because widening of the coronary arteries does not appear on day one. An electrocardiogram is recorded as well. One point is worth being clear about: a normal echocardiogram early in the illness neither excludes the diagnosis nor cancels the treatment.

There is also an incomplete form, with a persistent fever and fewer signs than the criteria ask for; babies are the likeliest to have it. In such cases the doctor leans on the blood tests and the echocardiogram and starts treatment without waiting for the full picture.

How it is treated

Kawasaki disease is treated in hospital and nowhere else; there is no home treatment for it. The mainstay is intravenous immunoglobulin, a solution of antibodies obtained from donor plasma. It damps down the inflammation in the vessel wall and cuts the chance of damage to the heart arteries several times over. It does most good when given within the first ten days of the illness; later it is still given, but the gain is smaller — hence all the urgency about the diagnosis.

The second medicine is acetylsalicylic acid, that is, aspirin. It is given first at an anti-inflammatory dose while the fever lasts, then at a low dose at which it stops platelets clumping together, and continued for several weeks, or longer if the arteries are affected. This is one of the few situations in which aspirin is prescribed to a child on purpose. Outside such a prescription, aspirin is not given to children and teenagers at all: it can cause Reye's syndrome, a rare but severe injury to the liver and brain. If a child on long-term aspirin catches chickenpox or flu, contact the doctor without waiting for the scheduled review; for the same reason the doctor may offer flu and chickenpox vaccination.

Improvement usually follows within a day and a half of the immunoglobulin infusion. If the fever persists, a second dose is given and corticosteroids are added, and in resistant cases medicines that block particular steps in the inflammation are used. That decision belongs to the hospital.

The heart afterwards and life beyond

The main complication is widening of the coronary arteries, that is, aneurysms. The vessel wall, weakened by inflammation, bulges under the pressure of the blood, and a clot forms more readily at that spot. Without treatment such changes appear in roughly one child in four; with immunoglobulin given in time, many times less often. Other large arteries such as the axillary or the femoral are affected less commonly. Small dilatations settle on their own over time in most children.

After discharge the child is followed up: the echocardiogram is repeated a few weeks later and then again, and if the heart is unaffected the aspirin is stopped and the follow-up gradually tails off. With persistent aneurysms the picture is different: medicines that reduce clotting are continued for a long time, anticoagulants may be added, follow-up with a paediatric cardiologist becomes permanent, and contact sports and heavy exertion are discussed case by case. In the rare event that an artery narrows or closes off, procedures on the heart vessels are used.

There is one practical detail parents often are not warned about: after immunoglobulin, live vaccines — measles and chickenpox — are put off for a while, because the donor antibodies stop them working. The doctor sets the interval and it is measured in months. The other vaccinations carry on as normal.

Children who come through Kawasaki disease with no consequences for the heart grow up and live like anyone else. Those whose arteries were affected are advised in adult life to watch blood pressure, cholesterol and weight more closely than most and not to smoke: the inflammation they went through adds cardiovascular risk for decades. The disease comes back only rarely, but it does happen, so a new prolonged fever in such a child is assessed with particular care.

Online consultation

An online appointment is useful at exactly the point where the picture is still unclear: the child has had a fever for several days, a rash or red eyes have appeared, and it is not obvious whether to wait or to act. The doctor will go through how many days the fever has run, what has been given and with what effect, ask to see the eyes, lips, tongue, palms, soles and the site of the vaccination scar, and say the essential thing — whether this can be watched at home or the child needs to be examined in person the same day. They will also help avoid missing the incomplete form in a baby, where the signs are few and so is the time. After discharge, an online appointment is a good place to go through the hospital summary: how long the aspirin continues, when the repeat echocardiogram is due, when vaccinations and PE can resume, and what to do if the child catches chickenpox while on aspirin. But Kawasaki disease itself is treated in hospital, and if a child is deteriorating quickly nobody waits for an online consultation — you call an ambulance.

This material is for information only and does not replace medical advice.