FCN1 and microscopic polyangiitis: We previously reported that the FCN1 mRNA level is elevated in peripheral blood mononuclear cells (PBMCs) of patients with vasculitis, including Takayasu arteritis (TA) and microscopic polyangiitis (MPA); specifically, we observed elevated expression of FCN1 in macrophages in the inflamed regions of surgical aorta specimens from TA patients14 and surgical glomeruli specimens taken from MPA patients15.