Primary and Secondary Thrombotic Microangiopathy Referred to a Single Plasma Exchange Center for Suspected Thrombotic Thrombocytopenic Purpura: 2000-2011

Abstract

Background: Patients who present with unexplained thrombocytopenia, that is, hemolytic anemia with end-organ dysfunction with a normal coagulation profile are suspected to have thrombotic thrombocytopenic purpura (TTP) and are usually referred to a plasma exchange (PE) center for immediate treatment to prevent mortality. Here, we describe the distribution and outcomes of patients with suspected TTP referred to a single center for PE therapy. Methods: In this retrospective cohort study, we reviewed the data of all consecutive patients who were treated with PE for suspected TTP at our center between January 2000 and December 2011 (Canada). Patients were followed for a median of 73 months. Results: Of 137 patients, 70 (51%) were determined to have primary (idiopathic) TTP and 67 (49%) secondary TTP or hemolytic uremic syndrome (HUS). Patients with primary TTP were twice as likely to be refractory than those with secondary TTP or HUS: 27 vs. 12%; p = 0.03. Patients with primary TTP were more likely to experience remission (61/70 (87%) vs. 45/67 (67%); p = 0.01); however, the relapse rate was higher in patients with primary versus secondary TTP-HUS: 11 vs. 1.5%, respectively (p = 0.03). The overall mortality rate was 23% (13 vs. 33% in those with primary vs. secondary TTP-HUS; p = 0.007). After excluding deaths from scleroderma renal crisis (100% mortality), malignancy (75% mortality) and stem cell transplant (50% mortality), the survival rate for secondary TTP was 85%. Conclusions: In contrast to patients with secondary TTP or HUS, those with primary TTP have a higher refractory and relapse rate, but are also more likely to achieve remission and survive.

Treatment and Outcome of Primary and Secondary Thrombotic Microangiopathies

“…The remission rate for patients with acquired idiopathic TTP in the presented cohort after TPE was 87%, and approximately 75% of the patients maintained this response during a median follow-up of 73 months [4] . Since the ADAMTS13 activity, antigen and inhibitor concentrations were not tested neither at diagnosis nor during the follow-up, the authors could not display the follow-up data on that [4] .…”

“…In the cohort of Dahlan et al [4] , nearly half of the patients had no identifiable cause, whereas the other half were found to be with some medical conditions, mainly including infections, drug use, malignancies. Among the cases with secondary TMAs, 10 patients had confirmed HUS secondary to Shiga toxin-producing Escherichia coli O157:H7, of which nine fully recovered with TPE, whereas one died due to brain stem infarction.…”

“…Drug-induced TMA was identified among 17 patients, and 12 patients had an underlying malignancy (both hematological and solid tumors) [4] . In patients with druginduced TMA, nearly 30% of them died, whereas the remaining 12 survived, of which some fully recovered and some went into remission with renal and neurological sequelae.…”

“…In this issue of American Journal of Nephrology , Dahlan and colleagues shared their experience in 137 patients with primary and secondary TMAs, which were referred to their center for suspected TTP and received therapeutic plasma exchange (TPE) as a first-line treatment for over a decade [4] . The authors displayed the demographic data of the patients as well as the treatment modalities and outcomes.…”

“…Since the ADAMTS13 activity, antigen and inhibitor concentrations were not tested neither at diagnosis nor during the follow-up, the authors could not display the follow-up data on that [4] .…”