Kawasaki disease is an acute vasculitis of childhood characterized by high fever, rash, bilateral nonexudative conjunctival injection, erythema of the oral mucosa, unilateral cervical lymphadenopathy, and erythema and edema of the hands and feet in the acute phase, or periungual desquamation in the subacute phase. Patients who lack full features of Kawasaki disease may have incomplete Kawasaki disease. Whereas the presenting signs of Kawasaki disease are transient, long-term morbidity and mortality may ensue because of an associated necrotizing arteritis that causes coronary artery aneurysms. Indeed, Kawasaki disease has replaced rheumatic fever as the leading cause of acquired heart disease in children in low- and middle-income countries.
There are no pathognomonic signs and no laboratory tests specific for diagnosis of Kawasaki disease. Despite almost 5 decades of research, its etiology is unknown. This has led many experts to posit that Kawasaki disease is an immune response that may be initiated by a variety of agents in genetically susceptible children. Investigators have focused on the association of temporal clusters of Kawasaki disease with environmental factors, including wind patterns, climate dynamics, and atmospheric counts of biological particles (Sci Rep 2011;1:152) (PLOS ONE 2018;13:e0191087) (Sci Rep 2018;8:16140).
Whereas earlier studies have examined the environmental factors associated with clusters of Kawasaki disease cases, Burns et al analyze differences in the patterns of clinical and laboratory findings in patients within temporal clusters in the current volume of The Journal. Clusters can occur by chance alone, so the authors use sophisticated epidemiological and statistical techniques to compare the features of cases within and across clusters, as well as those occurring outside of clusters. Cases occurring within a cluster had demographic, clinical, and laboratory features that were more similar to each other than would be expected by chance. The authors suggest that the similarity of within-cluster patient characteristics could reflect different etiologies in disease clusters, for example, varying triggers for Kawasaki disease or different intensity of exposures. Future investigation of patients within clusters, for example through their antibody responses or unique environmental exposures, may reveal a range of etiologies for this still-mysterious disease.
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