Kawasaki's disease is an uncommon illness in children that is characterized by high fever of at least five days' duration together with at least four of the following five findings:
- Inflammation with reddening of the whites of the eyes (conjunctivitis) without pus.
- Redness or swelling of the hands or feet, or generalized skin peeling.
- Lymph node swelling in the neck.
- Cracking inflamed lips or throat, or red "strawberry" tongue.
The above criteria are used to make a diagnosis of Kawasaki's disease. The terminology "incomplete Kawasaki's disease" is sometimes used for patients with only some features of classical Kawasaki's disease.
Kawasaki disease typically affects children under 5 years of age. Only rarely does it affect children over 8 years of age, in which case it is sometimes referred to as atypical Kawasaki's disease.
How can Kawasaki's disease cause serious complications?
Children with Kawasaki's disease can develop inflammation of the arteries of various parts of the body. This inflammation of the arteries is called vasculitis. Arteries that can be affected include the arteries that supply blood to the heart muscle (the coronary arteries). Vasculitis can cause weakening of the blood vessels and lead to areas of vessel widening (aneurysms). Coronary aneurysms have been reported in up to 25% of those with Kawasaki's disease.
Because of the potential for heart injury and coronary aneurysms, special tests are performed to examine the heart. Children are typically evaluated with an electrocardiogram (EKG) and an ultrasound test of the heart (echocardiogram). Other arteries that can become inflamed include the arteries of the lungs, neck, and abdomen. These effects can lead to breathing problems, headaches, and pain in the belly, respectively.
The usual symptoms and signs of Kawasaki's disease include:
- reddening of the eyes,
- cracked and inflamed lips and mucous membranes of the mouth with an inflamed "strawberry" tongue,
- ulcerative gum disease (gingivitis),
- swollen lymph nodes in the neck (cervical lymphadenopathy),
- a rash that is raised and bright red.
The rash appears in a glove-and-sock fashion over the skin of the hands and feet. The rash becomes hard, swollen (edematous), and then peels off.
Like all autoimmune diseases, the cause of Kawasaki disease is presumably the interaction of genetic and environmental factors, possibly including an infection. The specific cause is unknown, but current theories center primarily on immunological causes for the disease.
Evidence increasingly points to an infectious etiology, but debate continues on whether the cause is a conventional antigenic substance or a superantigen. Children's Hospital Boston reported that "some studies have found associations between the occurrence of Kawasaki disease and recent exposure to carpet cleaning or residence near a body of stagnant water; however, cause and effect have not been established".
An association has been identified with a SNP in the ITPKC gene, which codes an enzyme that negatively regulates T-cell activation. An additional factor that suggests genetic susceptibility is the fact that regardless of where they are living, Japanese children are more likely than other children to contract the disease. The HLA-B51 serotype has been found to be associated with endemic instances of the disease.
Kawasaki's disease is treated with high doses of aspirin (salicylic acid) to reduce inflammation and to mildly thin the blood to prevent blood clot formation. Also used in treatment is gamma globulin administered through the vein (intravenous immunoglobulin or IVIG), together with fluids.
This treatment has been shown to decrease the chance of developing aneurysms in the coronary arteries. Sometimes cortisone medications are given. Persisting joint pains are treated with anti-inflammatory drugs, such as ibuprofen (Advil) or naproxen (Aleve).
Plasma exchange (plasmapheresis) has been reported as effective in patients who were not responding to aspirin and gammaglobulin. Plasmapheresis is a procedure whereby the patient's plasma is removed from the blood and replaced with protein-containing fluids.
By taking out portions of the patient's plasma, the procedure also removes antibodies and proteins that are felt to be part of the immune reaction that is causing the inflammation of the disease. Kawasaki's disease that is not responding to the traditional aspirin and gammaglobulin treatments can be deadly. Medications that block the effects of TNF (tumornecrosis factor), one of the messenger molecules in the inflammatory response, are being studied for use in these situations.
Examples of TNF-blocking drugs are infliximab (Remicade) and etanercept (Enbrel). Further research is needed to design treatment programs for those who are failing conventional treatments. Pentoxifylline (Trental) is also being studied as a possible treatment for Kawasaki's disease.