cardiac complications Depending on the series, between 10% and 60% of children who develop coronary aneurysms never meet clinical criteria for KD The 2017 guidelines of the American Heart Association (AHA) provide a useful framework for managing children with suspected KD who not meet criteria for the diagnosis (see Fig 101.15 and also section on Incomplete KD below) Clinical manifestations of KD tend to be most incomplete and atypical in the youngest patients, the subgroup at highest risk for development of coronary artery abnormalities Infants younger than months are at particularly high risk Thus, KD should be considered in any infant with prolonged, unexplained fever In contrast, alternative explanations for the child’s symptoms must be carefully excluded before treating empirically with IVIG Consideration should be given to referring children to a regional KD center for further evaluation when the diagnosis is unclear At the other end of the spectrum, older children and adolescents with KD appear to be at increased risk for developing coronary aneurysms; however, older age at presentation is also associated with delayed diagnosis, which is known to incur significant risk Unlike infants, in whom the clinical findings of KD are often incomplete, older children appear to present with fairly typical manifestations Diagnosis may be delayed because clinicians are less likely to consider the diagnosis in older patients because most cases involve young children Further, children older than years of age frequently exhibit GI and meningeal symptoms, potentially clouding the diagnostic picture In any event, whether KD is indeed more aggressive in older children, or simply because diagnosis is more likely to be delayed, pediatricians must consider KD as a possible cause of prolonged fever in young people of any age