FCN1 and microscopic polyangiitis: Given that FCN1 mRNA is up-regulated in PBMCs of vasculitis patients (TA and MPA), and immunostaining revealed augmented expression of FCN1 in macrophages in the inflamed regions of surgical specimens of TA and MPA patients14, 15, augmented FCN1 levels in both PBMCs (Fig. 3) and serum of KD patients (Fig. 4) suggest that FCN1 is somehow related to the pathogenesis of vasculitis in KD.