Background: A specific diagnostic test for Kawasaki disease (KD) is currently unavailable. Redness or crust formation at the Bacille Calmette-Guérin (BCG) inoculation site is listed as a positive sign in the diagnostic guidelines of KD. The purpose of this study was to investigate the epidemiologic features of KD patients with such changes at the BCG inoculation site and to evaluate the specificity of this sign in KD diagnosis.
Methods: Data on KD patients who received BCG vaccination were analyzed from a Japanese nationwide epidemiologic survey on KD conducted in 2007. Patients who had 5 or 6 principal signs (complete cases) with redness or crust formation at the BCG inoculation site were compared by sex, year of hospital visit, day of first hospital visit, recurrent status, and presence of KD in siblings. To evaluate the specificity of the sign for KD diagnosis, patients aged 2 years or younger who were diagnosed as having respiratory syncytial virus or rotavirus infection using a commercial rapid test and who required hospitalization were observed.
Results: Of the 15,524 KD patients with a history of BCG vaccination, 7745 (49.9%) had redness or crust formation at the BCG inoculation site. This was observed in more than 70% of complete KD patients aged 3 to 20 months. Of these patients, the proportion with this sign in the group whose first day of hospital visit was within 1 to 4 days from the onset was significantly larger than that of the other patients groups (5–9 or 10+ days) (52.1%, P < 0.001). Among the patients with respiratory syncytial virus or rotavirus infection, none showed these changes at BCG inoculation site.
Conclusions: Redness or crust formation at the BCG inoculation site is a useful diagnostic sign for KD among children aged 3 to 20 months in countries with a BCG vaccination program. Even if patients have 4 or fewer signs of the clinical criteria for KD, physicians should consider that patients with redness or crust formation at the BCG inoculation site could suffer from KD.