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Introduction

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Kawasaki disease is a vasculitis of early childhood that has a propensity for affecting the coronary arteries. It is characterized by a cluster of symptoms and signs, which lead to the diagnosis of Kawasaki disease. It poses a diagnostic quandary for the primary physician because Kawasaki disease often mimics more common childhood illnesses presenting with fever. Moreover, in recent years, Kawasaki disease has presented in an atypical manner, making early diagnosis quite difficult. Therefore, in the present era, a primary care physician should be armed with a high index of suspicion when evaluating a febrile, irritable child. Left untreated, almost 20% to 25% of children with Kawasaki disease may develop aneurysms of coronary arteries. In the United States, the incidence of coronary artery aneurysms decreased to less than 5% after use of intravenous immunoglobulin (IVIG) became more widespread in the 1990s.1

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Epidemiology

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The majority of cases of Kawasaki disease occur between 6 months and 5 years of age. In the United States, the incidence of Kawasaki disease is highest in children of Asian descent (32.5 per 100,000 children under 5 years) and lowest in Caucasians (9.1 per 100,000 children under 5 years). The incidence rates are intermediate in African Americans and Hispanics.2 Children under 1 year of age have an increased propensity to develop coronary artery aneurysms. Kawasaki disease is prevalent year round but is punctuated by seasonal surges in winter and spring. Recurrences in the same patient and occurrences in siblings are noted occasionally. The incidence of Kawasaki disease is higher in children of parents who themselves have a past history of Kawasaki disease, which suggests that there may be a genetic predisposition of a child to Kawasaki disease.3

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Pathogenesis

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The hunt for a causative agent of Kawasaki disease has failed to find a definite agent, despite extensive research over the past 4 decades. Nevertheless, the clinical features, the seasonal outbreaks, and other epidemiologic characteristics strongly point toward an infectious agent. However, cultures and serologic tests against bacterial and viral agents have not been able to isolate a causative agent.

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Theories

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Superantigen Theory
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In the mid-1990s, superantigens produced by group A Streptococcus pyogenes and Staphylococcus aureus were implicated as causative agents of Kawasaki disease.4 In the human body, in response to a conventional antigen, only a limited number of lymphocytes are activated, typically less than 1 cell per 10,000 lymphocytes. In contrast to conventional antigens, superantigens can lead to excessive stimulation of a larger number of lymphocytes (as many as 25% of circulating lymphocytes). This leads to uncoordinated and disproportionate release of inflammatory cytokines from activated T cells. The best characterized superantigens are the staphylococcal enterotoxins and the streptococcal pyrogenic exotoxins that trigger the staphylococcal and streptococcal toxic shock syndromes. Toxic shock syndrome and Kawasaki disease share many common clinical and ...

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