Objective To investigate whether redness and crusting at the bacille Calmette-Guérin inoculation site (BCGitis), identified during acute illness owing to Kawasaki disease (KD), is an independent risk factor for development of cardiac complications.

Design Retrospective cohort study using data from the nationwide KD survey in Japan.

Setting Survey respondents included hospitals specialising in paediatrics and hospitals with ≥100 beds and a paediatric department throughout Japan.

Patients We included 17 181 patients with KD across Japan during 2005–2006.

Main outcome measures BCGitis and cardiac complications resulting from KD.

Results BCGitis was identified in 7549 (44%) patients with KD. Compared with patients without BCGitis, those with BCGitis were younger, more likely to be male, less likely to have recurrent status and visited a hospital and underwent initial intravenous immunoglobulin (IVIG) treatment earlier after KD onset. In the unadjusted model, patients with BCGitis were significantly less likely to have cardiac complications (crude OR 0.81, 95% CI 0.71 to 0.92). However, after including treatment factors (days of illness at initial IVIG and treatment responsiveness) in the adjusted model, the association was no longer significant (adjusted OR 0.89, 95% CI 0.77 to 1.03), indicating that BCGitis was not an independent factor associated with cardiac complication and might be confounded by treatment factors.

Conclusions BCGitis was identified in comparatively early illness stages of KD. Our findings indicated that BCGitis was not an independent factor associated with developing cardiac complications but was confounded by prompt initial IVIG administration, which might result in successful treatment and prevention of cardiac complications.