Controversies in differentiating thrombotic thrombocytopenic purpura and hemolytic uremic syndrome. Shah NT, Rand JH. The Mount Sinai Journal of Medicine 2003;70(5):344-351.

ABSTRACT:

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 (PE) 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, the background on both entities is reviewed and the controversy in differentiating between them is described. In the U.S., approximately 1,000 new cases of TTP are diagnosed each year. The disease is uncommon in the elderly and in infants. There are two primary types of TTP: the single acute episode and chronic relapsing TTP. The acute episode is more common and severe. Diarrhea-associated HUS is more common in children and is usually self-limited, while sporadic, nondiarrhea-associated HUS is seen more commonly in adults. This is the type of HUS, which is difficult to distinguish from TTP. Because TTP can sometimes involve severe renal disease and HUS can involve extrarenal disease, the two disorders can be especially difficult to distinguish. Although the diarrhea-associated HUS is self-limited, patients with HUS require early and careful management of acute renal failure with fluid and electrolyte balance. Blood transfusions and hemodialysis are frequently required. In the adult form of HUS, fresh frozen plasma (FFP) infusion is recommended in addition, especially with neurological symptoms. TTP, on the other hand, responds well to PE and, if not immediately available, FFP may be used. Steroids have been shown to be effective as well. Other therapies have also shown some success. Further efforts in understanding the pathophysiology, and investigating novel therapeutic options by way of future clinical trials will help shed more light on these two disease entities.