Summary

Kawasaki disease (KD) is an acute, self-limited, systemic vasculitis of unknown aetiology, extremely rare in infants younger than 6 months old. Younger infants are more likely to present with incomplete KD (IKD) and are at higher risk of developing coronary abnormalities. An early and specific clinical sign, not included in the classical diagnosis criteria, but that can be very useful in the diagnosis of KD, is the reaction at the Bacillus Calmette-Guérin (BCG) inoculation site. We describe a case of a 4-month-old boy, fully immunised, whose BCG scar reactivation led to the diagnosis of IKD. This case-report emphasises the importance of BCG site reactivation in establishing a diagnosis of IKD that clinicians should be aware of, especially in countries where BCG vaccination is still part of the immunisation schedule.