A Complete Histologic Approach to Gastrointestinal Biopsy From Hematopoietic Stem Cell Transplant Patients With Evidence of Transplant-Associated Gastrointestinal Thrombotic Microangiopathy

Context.— Transplant-associated thrombotic microangiopathy is a serious complication of hematopoietic stem cell transplant that may progress to multi-organ dysfunction. Transplant-associated thrombotic microangiopathy may involve the intestinal vasculature (intestinal transplant-associated thrombotic microangiopathy [iTMA]), causing patients to experience debilitating symptoms of ischemic colitis, including disproportionately severe abdominal pain and gastrointestinal bleeding, requiring heavy narcotic use and frequent transfusion support. Pathophysiology remains poorly investigated but may include endothelial damage mediated by inflammatory markers and the complement system. Endoscopy of hematopoietic stem cell transplant patients often produces biopsy samples, in which mucosal lamina propria capillaries are sufficient for an evaluation of iTMA features. Objective.— To provide a detailed review of histologic features of iTMA. Data Sources.— We conducted a systematic review of studies assessing histologic features of iTMA. Studies were identified by PubMed search and included a cohort study performed by our group. Conclusions.— The histologic hallmark of iTMA is endothelial cell injury that leads to hemorrhage and thrombosis of the capillaries. Histologic features include endothelial cell swelling, endothelial cell separation, perivascular mucosal hemorrhage, intraluminal schistocytes, intraluminal fibrin, intraluminal microthrombi, loss of glands, and total denudation of mucosa. Identification of features consistent with iTMA has immediate implications for clinical management that could potentially improve outcome and survival.