Hoshino S, et al. - Given coronary artery aneurysms and myocarditis represent well-known complications of Kawasaki disease (KD) but myocarditis results have not been systematically assessed in the subset presenting with low ejection fraction (EF), so, researchers investigated if late myocardial fibrosis could develop due to more severe myocardial inflammation as evidenced by low EF during the acute phase. They used late convalescent blood samples from 16 KD patients with an EF ≤ 55% on their initial echocardiogram and analyzed carboxyterminal propeptide of procollagen type I (PIPC), soluble suppressor of tumorigenicity 2, galectin-3 (Gal-3), growth-differentiation factor-15, and calprotectin via ELISA in those samples. For comparison, they used samples from gender- and age-matched KD patients with initial EF > 60%. They detected significantly high levels of Gal-3 and PIPC in convalescent KD patients with a history of low EF during the acute illness vs matched-control KD patients with normal EF. These findings foster concern for myocardial fibrosis as a potential late consequence of the more severe myocarditis experienced by a subset of KD patients during the acute phase.