Fig. 3

Chronologic pathology of gastrointestinal K-D as occurs in small- and medium-sized vessels within the subserosal fat: A Unlike the skin, no obvious small-vessel angiopathy of the mucosa occurs (H&E, ×10) B The incipient phase of the large-vessel arteriopathy is an accumulation of histiocytes and scavenger macrophages in the lumen and intima, along with intimal mucin deposition (H&E, ×10). C In the next phase of the progressive obliterative arteriopathy, the intima is expanded by inflammatory cells and mucin. There is variable fibrin deposition with some vessels showing a frank obliterative fibrin thrombus (H&E, ×10). D Reduction and progressive expansion of the intima occurs with a likely type I interferon effect as illustrated by the alcian blue stain (H&E, ×10). E MXA mirrors C5b-9 deposition (MXA, ×40) F. C5b-9 deposition (C5b-9, ×10). G Ultimately, the lumen is obliterated by loose matrix and a thrombus composed of collagen, mucin, and macrophages. This end-stage acellular collagenous plug obliterating the vascular lumen is highly specific to K-D (H&E, ×10). H Within the subserosa, an increase in collagen and mucin defines the key extravascular fibrosing and mucinous reaction of K-D (H&E, ×4)