Retrospective Analysis of Patients Afflicted with Thrombotic Thrombocytopenic Purpura: A Single Institutional Experience.

Abstract 2200 Introduction: Thrombotic Thrombocytopenic Purpura (TTP) is an acute life threatening condition characterized by thrombocytopenia, microangiopathic hemolytic anemia, with or without renal failure or neurologic abnormalities, and without another cause for thrombotic microangiopathy. The majority of cases of TTP are associated with a low ADAMTS13 activity which results from antibody to this enzyme. A minority of patients have TTP secondary to congenital deficiency of this enzyme. The mainstay of therapy for TTP is plasmapheresis (PEX) which has increased survival in affected patients from 10% to more than 75%. While TTP is considered as an uncommon disorder, at our institution we suspected that the diagnosis was made more commonly. Therefore we set out to perform a retrospective analysis of cases of TTP to evaluate cases diagnosed over the past 10 years. Methods: We performed a retrospective analysis of all cases of microangiopathy undergoing pheresis at our institution for presumed TTP from May 2007 to April 2012. A total of 112 patients had PEX initiated for presumed TTP however 11 of these were later determined to have some other etiology causing the constellation of symptoms and PEX was discontinued. The remaining 101 patients were entered into a database and further analyzed. Demographically, we captured patients from 30 of the 100 North Carolina counties because 3 other institutions in our state perform plasma exchange for TTP. ADAMTS13 activity and inhibitor levels were measured in 69 out of 101 patients. In our registry there were 80 patients with Idiopathic TTP and 21 patients with secondary TTP. Patients with idiopathic TTP were further divided based on the ADAMTS13 activity. Results: | Features | Idiopathic TTP (80) | Secondary TTP(21) | Idiopathic TTP ADAMTS13 10% (16) | Idiopathic TTP ADAMTS13 Unkwn(33) | |:-------------------------:| ------------------- | ----------------- | --------------------------------- | --------------------------------- | --------------------------------- | | Age (median) | 47 (17-80) | 43 (17-69) | 45 (23-78) | 50 (21-65) | 42 (21-79) | | Sex (%females) | 66 | 57 | 67 | 68 | 63 | | Race (%African American) | 72 | 76 | 67 | 62 | 81 | | Bld Grp (most frequent) | A+, 0+ | A+,O+ | A+ | O+ | A+ | | Symptoms (most freque | CNS, GI | CNS | CNS | CNS | CNS | | Hematocrit (median) | 36 (12-39) | 23 (15-37) | 24.5 | 25 | 26 | | Platelet (median) | 16000 | 17000 | 11000 | 48000 | 17000 | | LDH (median) | 1216 | 1109 | 1387 | 1161 | 1255 | | Creatinine (median) | 1.5 | 1.4 | 1.2 | 3.9 | 2.1 | | PEX (median) | 21 (3-160) | 21 (5-128) | 23 (8-91) | 12 (7-100) | 27 (3-64) | | Rituximab (no of pts) | 18 | 1 | 17 | 2 | | | Relapse (%) | 21 | 28 | 25 | | 30 | | >=1 relapse (no of pts) | 9 | 4 | NA | NA | NA | | Death (%) | 5 | 4 | 3 | | 9 | | ADAMTS 13<10%(%) | 38 | 28 | NA | NA | NA | | Inhibitor (present or Abs | 24 | 3 | NA | NA | NA | | ADAMTS 13>10%(%) | 20 | 14 | NA | NA | NA | | ADAMTS 13 Unknwn | 38 | 57 | NA | NA | NA | | Idiopathic TTP (%) | NA | NA | 38 | 20 | 38 | | Secondary TTP(%) | NA | NA | 28 | 14 | 57 | Discussion: Our analysis demonstrated that TTP was more common in females, African American population with a median age group in the mid forties with neurological symptoms being the predominant symptom of presentation. While hematocrit was higher in patients with idiopathic TTP these patients were noted to have increased incidence of ADAMTS13 levels less than 10% with inhibitors as compared to those with secondary TTP. Idiopathic TTP patients had more incidence of multiple relapses and required more Rituximab in addition to PEX. We compared our results with the results published from the Oklahoma registry. Similar to the Oklahoma registry results patients with ADAMTS13 levels less than 10% had more severe thrombocytopenia, renal dysfunction, required more sessions of PEX, had higher relapses and percentage of death compared to patients with idiopathic TTP with ADAMTS13 levels more than 10%. Patients with ADAMTS13 less than 10% required more Rituximab during first diagnosis of idiopathic TTP. In this group blood group A+ was seen more often whereas blood group O+ was prevalent in the group with ADAMTS more than 10%. Comparison amidst these groups brought out similarities between two distinct registries in the US. Our registry is another large registry of patients similar to the Oklahoma TTP registry. While many similarities are seen with the Oklahoma group there were a few differences as cited above. Disclosures: No relevant conflicts of interest to declare.