Kidney biopsies, where obtained during acute and post-acute iHUS reveal varied features [25, 33, 37, 38, 92, 93] that replicate key findings described in other forms of HUS [3], including endothelial cell swelling and luminal narrowing, focal mesangiolysis, intravascular deposition of fibrin, and diffuse granular staining for C3 [25, 33, 37, 92, 93], and in some cases, for IgG or IgM [25, 37, 92]. The gene discussed is CD40LG; the disease is hemolytic-uremic syndrome.