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 FIGURE 101.15 Evaluation of suspected Kawasaki disease KD, Kawasaki disease; CRP, C-reactive protein; ESR, erythrocyte sedimentation rate; ALT, alanine aminotransferase; WBC, white blood cell; hpf, high-powered field; echo, echocardiogram (Adapted with permission from Sundel RP Kawasaki disease: Clinical features and diagnosis In: Post TW (Ed), UpToDate Waltham, MA Accessed March 4, 2019 Copyright ©2019 UpToDate, Inc For more information visit www.uptodate.com ) No laboratory studies are included in the diagnostic criteria for KD, but certain findings may support the diagnosis Most characteristic is systemic inflammation, with widespread elevation of acute-phase reactants (including CRP and ESR), leukocytosis, and a left shift in the white blood cell count By the second week of illness, platelet counts also rise, reaching 1,000,000/mm3 in the most severe cases Thrombocytopenia is a poor prognostic factor and may indicate platelet consumption Children with KD often present with a normocytic, normochromic anemia; hemoglobin concentrations more than two standard deviations below the mean for age are noted in approximately one-half of patients within the first weeks of illness Urinalysis commonly reveals white blood cells on microscopic examination; the cells are mononuclear, and so are not detected by dipstick tests for leukocyte esterase They also originate in the urethra, so they will be missed on urinalyses obtained by bladder tap or catheterization, so a clean catch is preferred Measurement of liver enzymes often reveals elevated transaminase levels or mild hyperbilirubinemia due to intrahepatic congestion In addition, a minority of children may develop obstructive jaundice from hydrops of the gallbladder If sampled, other body fluids demonstrate inflammation as well: CSF typically displays a mononuclear pleocytosis (