Clinicopathological manifestations and treatment of intestinal transplant-associated microangiopathy

Intestinal transplant-associated microangiopathy (i-TAM) is an important complication after allogeneic hematopoietic SCT. From 1997 to 2006, 87 of 886 patients with diarrhea after transplantation received colonoscopic biopsy. i-TAM, GVHD and CMV colitis were diagnosed histopathologically. The median duration from transplantation to the onset of diarrhea was 32 days (range: 9-130 days) and that from the onset of diarrhea to biopsy was 12 days (range: 0-74 days). The median maximal amount of diarrhea was 2 l/day (range: 130-5600 ml/day). Histopathological diagnosis included i-TAM (n=80), GVHD (n=26), CMV colitis (n=17) and nonspecific findings (n=2) with overlapping. Among 80 patients with i-TAM, abdominal pain was a major symptom, and only 11 patients fulfilled the proposed criteria for systemic TAM. Non-relapse mortality (NRM) among patients without resolution of diarrhea was 72% and i-TAM comprised 57% of NRM. NRM was 25% among patients without intensified immunosuppression, but was 52, 79 and 100% among those with intensified immunosuppression before diarrhea, after diarrhea, and before and after diarrhea, respectively. In conclusion, i-TAM is a major complication presenting massive refractory diarrhea and abdominal pain, which causes NRM. Avoiding intensified immunosuppression that damages vascular endothelium until the resolution of i-TAM may improve transplant outcome.