Discrimination between incomplete and atypical Kawasaki syndrome versus other febrile diseases in childhood: results from an international registry-based study

OBJECTIVES: Kawasaki syndrome (KS) is an acute systemic vasculitis of unknown origin predominantly affecting young children. Early diagnosis is crucial to prevent cardiac complications. However, the differential diagnosis of patients with the incomplete or atypical form of the disease poses a heavy challenge for the paediatrician. Our aim was to evaluate the prevalence of incomplete and atypical cases among children with KS and to identify clinical and laboratory variables that may help differentiate incomplete and atypical KS from other febrile diseases at this age. METHODS: We established an international registry to recruit patients with KS, including those with incomplete and atypical forms. The control group included age-matched febrile children admitted to the hospital with a variety of diseases mimicking KS. The aim was to define clinical or laboratory clues to help in the discrimination of incomplete and atypical KS patients from others. RESULTS: Two hundred and twenty-eight patients with incomplete KS (78%) and atypical KS (22%) were compared to 71 children with other febrile diseases. Patients with incomplete and atypical KS presented a statistically significant higher frequency of mucosal changes, conjunctivitis, extremity abnormalities and perineal desquamation compared to the group of other febrile diseases. In addition, C-reactive protein and platelet counts were significantly higher in incomplete and atypical KS compared to the other group. CONCLUSIONS: This is the largest series of incomplete and atypical KS patients of non East-Asian ancestry: we suggest that in patients with the aforementioned clinical features and laboratory evidence of systemic inflammation in terms of increased C-reactive protein and platelet counts an echocardiogram should be performed and diagnosis of KS considered.