Kawasaki's disease

Kawasaki disease is a syndrome of unknown cause that results in a fever and mainly affects children under 5 years of age. It is a form of vasculitis, where blood vessels become inflamed throughout the body. The fever typically lasts for more than five days and is not affected by usual medications. Other common symptoms include large lymph nodes in the neck, a rash in the genital area, lips, palms, or soles of the feet, and red eyes. Within three weeks of the onset, the skin from the hands and feet may peel, after which recovery typically occurs. In some children, coronary artery aneurysms form in the heart.

While the specific cause is unknown, it is thought to result from an excessive immune system response to an infection in children who are genetically predisposed. It does not spread between people. Diagnosis is usually based on a person's signs and symptoms. Other tests such as an ultrasound of the heart and blood tests may support the diagnosis. Diagnosis must take into account many other conditions that may present similar features, including scarlet fever and juvenile rheumatoid arthritis. An emerging 'Kawasaki-like' disease temporally associated with COVID-19 appears to be a distinct syndrome.

Typically, initial treatment of Kawasaki disease consists of high doses of aspirin and immunoglobulin. Usually, with treatment, fever resolves within 24 hours and full recovery occurs. If the coronary arteries are involved, ongoing treatment or surgery may occasionally be required. Without treatment, coronary artery aneurysms occur in up to 25% and about 1% die. With treatment, the risk of death is reduced to 0.17%. People who have had coronary artery aneurysms after Kawasaki disease require lifelong cardiological monitoring by specialized teams.

Kawasaki disease is rare. It affects between 8 and 67 per 100,000 people under the age of five except in Japan, where it affects 124 per 100,000. Boys are more commonly affected than girls. The disorder is named after Japanese pediatrician Tomisaku Kawasaki, who first described it in 1967.

Signs and symptoms

Kawasaki disease often begins with a high and persistent fever that is not very responsive to normal treatment with paracetamol (acetaminophen) or ibuprofen. This is the most prominent symptom of Kawasaki disease, and is a characteristic sign that the disease is in its acute phase; the fever normally presents as a high (above 39–40 °C) and remittent, and is followed by extreme irritability. Recently, it is reported to be present in patients with atypical or incomplete Kawasaki disease; nevertheless, it is not present in 100% of cases.

The first day of fever is considered the first day of the illness, and its duration is typically one to two weeks; in the absence of treatment, it may extend for three to four weeks. Prolonged fever is associated with a higher incidence of cardiac involvement. It responds partially to antipyretic drugs and does not cease with the introduction of antibiotics. However, when appropriate therapy is started – intravenous immunoglobulin and aspirin – the fever subsides after two days.

Bilateral conjunctival inflammation has been reported to be the most common symptom after fever. It typically involves the bulbar conjunctivae, is not accompanied by suppuration, and is not painful. This usually begins shortly after the onset of fever during the acute stage of the disease. Anterior uveitis may be present under slit-lamp examination. Iritis can occur, too. Keratic precipitates are another eye manifestation (detectable by a slit lamp, but are usually too small to be seen by the unaided eye).

Kawasaki disease also presents with a set of mouth symptoms, the most characteristic of which are a red tongue, swollen lips with vertical cracking, and bleeding. The mucosa of the mouth and throat may be bright red, and the tongue may have a typical "strawberry tongue" appearance (marked redness with prominent gustative papillae). These mouth symptoms are caused by necrotizing microvasculitis with fibrinoid necrosis.

Cervical lymphadenopathy is seen in 50% to 75% of children, whereas the other features are estimated to occur in 90%, but sometimes it can be the dominant presenting symptom. According to the diagnostic criteria, at least one impaired lymph node ≥ 15 mm in diameter should be involved. Affected lymph nodes are painless or minimally painful, nonfluctuant, and nonsuppurative; erythema of the neighboring skin may occur. Children with fever and neck adenitis who do not respond to antibiotics should have Kawasaki disease considered as part of the differential diagnoses.

In the acute phase of the disease, changes in the peripheral extremities can include erythema of the palms and soles, which is often striking with sharp demarcation and often accompanied by painful, brawny edema of the dorsa of the hands or feet, so affected children frequently refuse to hold objects in their hands or to bear weight on their feet. Later, during the convalescent or the subacute phase, desquamation of the fingers and toes usually begins in the periungual region within two to three weeks after the onset of fever and may extend to include the palms and soles. Around 11% of children affected by the disease may continue skin-peeling for many years. One to two months after the onset of fever, deep transverse grooves across the nails may develop (Beau's lines), and occasionally nails are shed.

The most common skin manifestation is a diffuse macular-papular erythematous rash, which is quite nonspecific. The rash varies over time and is characteristically located on the trunk; it may further spread to involve the face, extremities, and perineum. Many other forms of cutaneous lesions have been reported; they may include scarlatiniform, papular, urticariform, multiform-like erythema, and purpuric lesions; even micropustules were reported. It can be polymorphic, not itchy, and normally observed up to the fifth day of fever. However, it is never bullous or vesicular.

In the acute stage of Kawasaki disease, systemic inflammatory changes are evident in many organs. Joint pain (arthralgia) and swelling, frequently symmetrical, and arthritis can also occur. Myocarditis, diarrhea, pericarditis, valvulitis