Kawasaki Disease (KD), also known as mucocutaneous lymph node syndrome, is an acute, febrile, multisystem illness that primarily affects young children.

Its most serious complications are the result of systemic vasculitis.

The peak incidence of KD is between 1 and 2 years of age and mostly occurs before 5 years of age. It is more common in boys.

In the United States, children of Asian ancestry are affected six times more often than are white children.

KD occurs sporadically and in epidemics. A seasonal predilection has been observed, with cases occurring more often in the winter and spring.

KD is a generalized vasculitis that involves small- to medium-sized arteries.

Although the exact cause of KD is unknown, it is most likely the result of a superantigen produced by an infectious agent such as Staphylococcus aureus, resulting in massive cytokine release.

Fever. Usually marks the onset of KD and is present for at least 5 days straight. Elevated temperature shows a remittent pattern, with spikes to 103°F and even up to 105°F. The average duration of the fever is 11 days.

Cervical lymphadenopathy. A single, enlarged, nonsuppurative lymph node on the side of the neck (cervical chain) is the least common diagnostic feature of KD, seen in 75% of patients.

Bilateral conjunctival injection. Characterized by bilateral, nonpurulent, limbic sparing conjunctival injection. Patients may exhibit signs of photophobia (Fig. 10.3).

Oral mucous membrane changes. The earliest manifestations are seen on the lips, with bright red erythema accompanied by fissuring and swelling. Prominent papillae create the appearance of a “strawberry tongue” (Fig. 10.4). Examination of the oropharynx reveals a diffuse erythema without vesicles, erosions, or ulcers.

Changes in the extremities. An intense erythema appears on the palms and soles on days 3 to 5 of the illness, followed by an indurated edema. A sharp demarcation may be seen at the wrists and the sides of the hands and feet.

Polymorphous rash. The truncal rash of KD is polymorphous and can be macular, papular, urticarial, erythrodermatous, targetoid, or composed of fine micropustules, but it is never vesicular or bullous. The eruption is usually pruritic and favors the trunk and proximal extremities, but it may be generalized (Fig. 10.5).

The presence of scarlatiniform erythema in the perianal or inguinal area may be a useful diagnostic sign. The rash in this area progresses to desquamation before the palms and soles begin to peel (Fig. 10.6).

Cardiac involvement is the most worrisome complication of KD.

During the acute phase of the illness, tachycardia may develop, with gallop rhythm, subtle electrocardiographic changes, pericardial effusion, tricuspid insufficiency, or mitral regurgitation.

Coronary artery aneurysms have been reported to occur in approximately 25% of untreated patients and may result in thrombosis with subsequent infarction.

The diagnosis of KD is based on recognition of its clinical features and is supported by compatible laboratory findings.

Diagnosis requires fever persisting 5 days or more plus 4 out of 5 of the following features:

• Polymorphous rash

• Bilateral conjunctival injection

• Oral mucous membrane changes

• Cervical lymphadenopathy

• Changes of peripheral extremities: Erythema of palms and soles, indurative edema of the hands and feet, desquamation of the fingertips.

During the acute phase of the illness, leukocytosis with a predominance of immature and mature granulocytes is common, with 50% of patients having a white blood cell count >15,000/mL.

Nonspecific abnormalities of acute phase reactants, such as the erythrocyte sedimentation rate and C-reactive protein levels are usually present.