The principal pathologic feature of Kawasaki disease (KD) is an acute vasculitis that affects the microvessels (arterioles, venules, and capillaries) anywhere in the body.
Since there are no pathognomonic laboratory findings, the diagnosis is established clinically by the presence of fever and at least four of five clinical features (conjunctival injection, oropharynx erythema, cervical adenopathy, hand and foot erythema/swelling, and rash).
As many as 20% of children will have incomplete KD, with only two of the conventional diagnostic criteria. Elevated C-reactive protein or erythrocyte sedimentation rate should raise suspicion in these children and consultation with a local expert is advised.
Positive screening tests for an infectious etiology of an acute illness may identify a concomitant infection, carrier state, or viral shedding and therefore may not exclude a diagnosis of KD.
All patients diagnosed with Kawasaki syndrome should be hospitalized for administration of intravenous gamma globulin (IVIG), aspirin therapy, and cardiac evaluation.
The overall mortality rate of Kawasaki syndrome in American children ranges from 0.1% to 0.2% and peaks between 15 to 45 days after the onset of fever. Patients receiving treatment within the first 8 to 10 days of the onset of fever have the best prognosis.
KD, or mucocutaneous lymph node syndrome, is an acute, self-limited, multisystem vasculitis of unclear etiology. KD is the leading cause of acquired heart disease in children in the United States and Japan. The diagnosis of classical disease is based upon clinical criteria; there are no pathognomonic laboratory findings. This vasculitis affects nearly every organ system in the body. First-line treatment is IVIG, which has been shown to reduce the risk of coronary artery aneurysm from 25% to 5%.
Etiology and Pathogenesis
Although an etiology is unknown, it has been hypothesized that KD may be a unique response of genetically predisposed individuals to some unidentified microbial agent. Alternatively, KD may be an unexplained immunologic response to known microbial agents. Environmental toxins have been suggested but never proven as having a role.1 The principal pathologic feature of this syndrome is an acute, nonspecific vasculitis that affects the microvessels (arterioles, venules, and capillaries). Nearly every organ system is involved. In the heart, the vasculitis results in coronary aneurysm formation in 20% to 25% of untreated patients.
Cases usually occur in clusters throughout the year, particularly during winter and spring. The peak incidence is in children 18 to 24 months of age, with 80% to 85% of cases occurring in children younger than 5 years. It is most common in children of Asian and Pacific Island descent and more common in males than females (1.5:1).1,2
The diagnosis of KD is established using clinical criteria: presence of fever for 5 days and four of five other physical findings (Table 62-1).