Identification and Treatment of Thrombotic Microangiopathies in Allogeneic Stem Cell Transplants

Study Summary

Mortality in the major thrombotic microangiopathies (TMAs), TTP and aHUS, exceeds 90% unless rapidly diagnosed and appropriately treated. TMAs complicate 10-20% of allogeneic bone marrow hematopoietic stem cell transplants (alloHSCT), conveying inferior survival. Multiple etiologies have been proposed for these transplant-associated TMAs (TA-TMAs), but once infection, graft vs. host disease (GvHD), and drug effects have been ruled out, most are treated as TTP-like disorders using plasma exchange (PEx). But PEx has no impact on mortality in this setting. Clear definition of the pathophysiology of the TA-TMAs is required to guide effective treatment. Investigators hypothesize that an aHUS-type TMA, related to dysregulation of the alternative complement pathway, is involved and will be characterized by elevated plasma levels of C5b-9 and detectable C5b-9 deposition in bone marrow sinusoidal vessels. Investigators further hypothesize that treatment with inhibitors of terminal complement components will reverse the TMA in vivo, and block endothelial cell damage in our in vitro model systems. The data investigators generate from this observational study of TA-TMAs should enable prediction of their development prior to overt clinical manifestations, and guide appropriate therapy.

Primary Outcome

Per protocol a thrombotic microangiopathy is defined as development of: * increase in number of schistocytes per high power microscopic field from baseline * increase in baseline level of anemia, measured by hemoglobin decline, which must be Coombs negative * unexplained doubling from baseline of serum LDH

Interventions

• DRUG eculizumab