Extracriteria manifestations in Kawasaki disease: coronary threat or diagnostic pitfall?

Kawasaki disease (KD) may present with manifestations beyond classical diagnostic criteria, but data on extracriteria manifestations as a multisystem phenotype remain limited. We aimed to assess the frequency and clinical significance of extracriteria manifestations in children with KD. In this retrospective single-center study, we reviewed 254 children with KD between January 2005 and December 2025. Extracriteria manifestations were defined as clinically documented organ-system involvement beyond the five principal diagnostic criteria of KD after exclusion of alternative diagnoses. Patients were compared according to extracriteria manifestations with respect to demographic, clinical, laboratory, echocardiographic, treatment, and coronary outcome variables. Extracriteria manifestations were identified in 77 patients (30.3%). Gastrointestinal involvement was most common (13.4%), followed by cardiovascular (non-coronary) and neurological involvement. Patients with extracriteria manifestations were more often female (46.8% vs. 32.8%), had higher C-reactive protein levels, more frequent hypoalbuminemia, lower serum sodium levels, and longer hospitalization (all p < 0.05). Although the median admission-to-diagnosis interval was similar between groups, its distribution differed significantly, suggesting that a subset of patients with extracriteria manifestations experienced longer diagnostic delays. Coronary involvement, IVIG resistance, and follow-up coronary outcomes were similar between groups. In multivariable analysis, female sex (OR 1.81, 95% CI 1.01-3.24) and higher C-reactive protein levels (OR 1.04, 95% CI 1.00-1.09) were independently associated with extracriteria manifestations.

Extracriteria manifestations are common in KD and are associated with greater inflammatory burden and longer hospitalization. Female sex and higher C-reactive protein levels were independently associated with extracriteria manifestations, whereas coronary involvement, IVIG resistance, and follow-up coronary outcomes were similar between groups. Early recognition of these presentations may facilitate timely diagnosis and management.

• Kawasaki disease is a systemic vasculitis involving multiple organ systems beyond classical criteria, but reported frequencies vary widely due to inconsistent definitions. • Extracardiac manifestations often overlap with incomplete presentations and can lead to significant diagnostic challenges and delays.

• Using a strict predefined definition, extracriteria manifestations were identified in 30.3% of patients; female sex and higher C-reactive protein levels were independently associated with extracriteria manifestations. • Extracriteria manifestations were associated with a greater inflammatory burden and longer hospitalization but not with coronary involvement, IVIG resistance, or adverse follow-up coronary outcomes.