Development of coronary artery lesions in indolent Kawasaki disease following initial spontaneous defervescence: a retrospective cohort study.

Background: No standard treatment protocol exists for Kawasaki disease (KD) after spontaneous defervescence that does not use intravenous immunoglobulin (IVIG). Moreover, some cases present an indolent course and later develop coronary artery lesions (CALs). We aimed herein to assess the short-term prognosis of KD after defervescence and to clarify the characteristics of indolent KD.

Study Design: The present report is the culmination of a 10-year retrospective cohort study of KD at two Japanese tertiary pediatric centers. Cases of spontaneously defervesced KD ≤ 7 days of illness without IVIG which were afebrile for ≥ 3 days were classified as 'defervesced KD' (dKD). Of these, cases which developed CALs, or received IVIG for ongoing systemic inflammation were sub-classified into the indolent KD group (iKD). The primary outcome was the prevalence of CALs.

Results: Among 968 KD patients, 7.3 % (71/968) fell into the dKD, and 11.2 % (8/71) into the iKD, groups. No difference in CAL prevalence was observed between the dKD group and the KD group treated with IVIG (9.9 % vs. 7.6 %, p value = 0.49). Six of the 8 iKD cases developed CALs between Days 11 and 23 (median 16) of illness. All iKD cases presented recurrent fever or re-elevated CRP; however, there were generally fewer persistent KD symptoms than at diagnosis.

Conclusions: The prognosis of spontaneously defervesced KD was relatively benign. However, indolent cases with ongoing, systemic inflammation developed CALs. In some cases, immediate IVIG use can be withheld as long as recurrent fever and re-elevation of CRP are monitored and supplementary echocardiogram are conducted.