A, B, C, and D: Skin histology pre-Eculizumab microvascular changes along with the pattern and extent of C5b-9 deposition and MXA expression in tissue. An erythematous lesion biopsied in July 2009 shows a thrombotic microangiopathy along with dermal chronic microvascular changes characterized by thickened basement membrane zones along with superficial vascular ectasia and foci of vascular drop out. The chronic microvascular changes are present in both the A (200x) and B (1000x) biopsies while intraluminal fibrin deposition is noted in B. (hematoxylin and eosin) In Figure 1A, there is a sparse perivascular lymphocytic infiltrate. The vessels appear hyalinized attributable to vascular basement membrane zone reduplication. In Figure 1B, the vessel is largely devoid of endothelium and contains a loosely adherent thrombus. The vessel is also noticeably thickened. Figure 1C exhibits the pattern of C5b-9 deposition pre-eculizumab. There is prominent deposition of C5b-9 by immunofluroescence in the vessels in the pre-eculizumab biopsy (400x). Figure 1D demonstrates MxA in skin biopsy pre-Eculizumab. There is extensive staining for MxA in the epidermis, endothelium and inflammatory cells in the pre-eculizumab biopsy indicative of a type I IFN rich microenvironment (diaminobenzidene, 1000x).