Controversies in differentiating thrombotic thrombocytopenic purpura and hemolytic uremic syndrome

The diagnoses of thrombotic thrombocytopenic purpura (TTP) and hemolytic uremic syndrome (HUS) often remain questionable, forcing the clinician to make the difficult decision of initiating therapy based on symptomatology and clinical judgment and, sometimes, instinct. An increased awareness of characteristic symptoms and early diagnoses of TTP and HUS are of utmost importance, given the excellent results obtained with prompt plasma exchange therapy. Tremendous progress has been made in understanding TTP and HUS since TTP was first described more than 75 years ago at Mount Sinai. However, several questions are still not definitively answered. In this article, we will review background on both entities, and then describe the controversy in differentiating between them.