Features of Kawasaki disease at the extremes of age

Aim:  The diagnosis of Kawasaki disease (KD) in those outside the typical age range (6 months−4 years) is often delayed, potentially worsening prognosis. The features of KD in children ≤6 months and ≥5 years were compared with those presenting within the more typical age distribution. Methods:  Korean children with complete diagnostic criteria for KD were grouped according to their age at presentation: Group A (≤6 months), Group B (7 months−4 years) and Group C (≥5 years). The clinical features, laboratory findings and outcome in each group were compared. Results:  Of 136 children presenting to a single centre between 1999 and 2003, 10 children were in Group A, 114 in Group B and 12 in Group C. The mean total fever duration was 8 days in Group C and 6.2 days in Group A ( P  = 0.03). All children in Group C had cervical lymphadenopathy, compared with 50% of Group A and 64% of Group B ( P  = 0.01). Coronary artery lesions were commoner in older children (Group C, 42%) compared with Group B (17%, P  = 0.05). All children had an equivalent leukocytosis, but Group C had significantly higher neutrophil counts ( P  = 0.001). Group A had significantly lower mean haemoglobin ( P  = 0.003) and total protein ( P  = 0.002) at presentation and a more marked thrombocytosis 1 week after intravenous immunoglobulin therapy ( P  < 0.05). Conclusion:  The clinical and laboratory phenotype of KD varies with age. Older children may have a more marked inflammatory response and worse outcome. Younger children who are treated appropriately may not have a chance to higher risk of coronary artery lesions.