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With prompt treatment, most children with Kawasaki disease make a full recovery. But sometimes complications can develop.

The complications associated with Kawasaki disease are mainly related to the heart.

They happen as a result of the inflammatory effect that the condition has on the blood vessels.

This sometimes affects blood vessels outside of the heart.

Inflammation in the blood vessels that supply blood to the heart (coronary arteries) can cause a section of the artery wall to weaken.

As the blood passes through the weakened part of the artery wall, the blood pressure causes it to bulge outwards like a balloon. This is called an aneurysm.

This can either cause:

  • a heart attack – where part of the heart muscle dies because it is starved of oxygen
  • heart disease – where the heart's blood supply is blocked or interrupted

Rarely, the aneurysm can burst (rupture), which could cause severe internal bleeding.

It's also possible for other major arteries to be affected, such as the brachial artery, the main blood vessel in the upper arm, or the femoral artery, the main blood vessel in the upper thigh.

Some aneurysms heal by themselves over time. But some children may experience further complications that require follow-up treatment with a specialist.

Around 1 in 4 children with Kawasaki disease who don't receive treatment – because the condition has been diagnosed incorrectly, for example – go on to experience heart-related complications.

The risk of developing complications is reduced for children who receive intravenous immunoglobulin (IVIG) to treat Kawasaki disease.

The heart-related complications associated with Kawasaki disease are serious and may be fatal in 2 to 3% of cases that go untreated.

Children under the age of 1 are known to be at higher risk of serious complications.

If your child develops a serious heart abnormality, they may require medicine or, in some cases, surgery.

Possible treatments include:

  • anticoagulant medicines and antiplatelet medicines – medicines that stop the blood clotting, which may prevent your child having a heart attack if their arteries are particularly inflamed
  • coronary artery bypass graft – surgery to divert blood around narrow or clogged arteries, and improve the blood flow and oxygen supply to the heart
  • coronary angioplasty – a procedure to widen blocked or narrowed coronary arteries to improve the blood flow to the heart; sometimes a short, hollow metal tube called a stent is inserted into the blocked artery to keep it open

Children with severe complications may have permanent damage to their heart muscles or valves, the flaps that control the flow of blood.

They'll have regular follow-up appointments with a heart specialist (cardiologist) so their condition can be closely monitored.

If your child has had heart complications as a result of Kawasaki disease, they have an increased risk of developing cardiovascular complications later in life.

This includes conditions such as heart attacks and heart disease.

If your child has had complications from Kawasaki disease, it's essential that they have follow-up appointments with a specialist.

The cardiologist will be able to advise you about your child's likelihood of developing further heart-related problems.