Bacillus Calmette-Guérin scar reactivation (BCGitis) in Kawasaki disease: a scoping review

The aim of this study is to map and synthesise the evidence on the scattered and heterogeneous reported prevalence of Bacillus Calmette-Guérin (BCG) scar reactivation (BCGitis) in Kawasaki disease (KD), examine clinical relationships, and identify knowledge gaps for future research. A scoping review was conducted according to the PRISMA-ScR guidelines. PubMed, Scopus, EMBASE, Web of Science, Cochrane Library, China National Knowledge Infrastructure (CNKI), and KoreaMed were searched for observational studies of BCG-vaccinated children with KD. We retrieved the prevalence of BCGitis and its relationship with age, sex, KD form, BCG vaccine strain, coronary artery abnormalities (CAA), and treatment response. Fifteen studies from five Asian countries (Japan, Korea, Taiwan, China, and Singapore), including 21,880 children with KD, were identified. The median reported prevalence of BCGitis was 37.5% (range, 3.5%-75.2%), driven by a few large studies. Its prevalence was 61.8% below 2 years and 9.1% over 2 years in 17,000 patients with KD. Its unweighted study-level prevalence (MU-SLP) was slightly higher in males than in females (49.8% vs. 46.1%), and in the largest number of patients with KF reported, it was associated with lower CAA rates of 11.6 vs.13.8% in the absence of BCGitis. No significant relationships were observed between KD type, vaccine strain, or treatment response.

Owing to the inherent methodology and limitations of scoping reviews, these findings should be interpreted as a map of the current evidence rather than a quantitative conclusion. BCGitis is a common manifestation of KD in BCG-vaccinated children and may have diagnostic value, particularly in younger children, in whom diagnosis may be difficult. Although it also seems to have prognostic value regarding the development of CAA, we urge caution because confounding cannot be ruled out. However, the current evidence lacks robustness due to the heterogeneity and design limitations of the studies. Future research addressing these limitations is required.

• Reactivation at the Bacillus Calmette-Guérin (BCG) inoculation site (BCGitis) has been reported in patients with Kawasaki disease (KD). • Its true prevalence remains unclear due to inconsistent reporting of BCG vaccination status or examination of the inoculation site.

• The unweighted study-level prevalence (MU-SLP) of BCGitis among children with KD and prior BCG vaccination was 38.6%. It is slightly higher in males and younger children but is not different between complete and incomplete KD, with coronary artery abnormalities (CAA) being more common in the absence of BCGitis. • Further studies are required to provide robust evidence for these findings.

Hassib Narchi and Alyson Skinner. Bacillus Calmette-Guérin scar reactivation (BCGitis) in Kawasaki disease. A Scoping Review. MedRxiv [preprint]. October 5, 2025. doi:  https://doi.org/10.1101/2025.10.03.25337219.