Dunn, Brianne L.

Abstract Abstract 2203 Background: Thrombotic thrombocytopenic purpura (TTP) is frequently characterized by severe ADAMTS13 deficiency, the cause of which is unknown. An important exception is ticlopidine-associated TTP (tc-TTP), the most common drug-induced TTP syndrome. In 1998, a possible association of TTP with ticlopidine was reported. In 1999, two additional series reported this association. In 2000, a fourth study reported severe A DAMTS13 deficiency among six of seven tc-TTP persons- suggesting a causal pathway. All of these reports were from the United States. Recently, we reported characteristics of 186 acquired idiopathic (ai)- TTP patients in Japan with severe ADAMTS13 deficiency, noting that clinical and laboratory findings for ai-TTP patients in Japan differed from those for cohorts of ai-TTP patients in Europe and North America- raising concern that TTP findings vary by region of the world. (PLOS One 2011) We now on report clinical and laboratory characteristics of a cohort of TTP patients from Japan with tc-TTP, and compare these findings to three cohorts of tc-TTP in the United States and one cohort of ai-TTP patients from Japan. Methods: We queried a database of thrombotic microangiopathy patients identified from a national TTP referral laboratory in Japan of cases identified between 1998 and 2008. Severe ADAMTS13 deficiency was characterized by activity levels < 5%. All tc-TTP patients and 186 of 911 ai-TTP patients in the database had severe ADAMTS13 deficiency and first onset of TTP. Comparisons were made to tc-TTP patients reported previously from the United States. Results: Characteristics of ai- TTP with severe ADAMTS13 deficiency in Japan and tc-TTP in Japan and US Conclusions: These data from Japan validate insights about tc-TTP initially proposed in 1998, 1999, and 2000 in the United States. Ticlopidine is a likely cause of TTP, the mechanism is via a cross-reactive antibody to ADAMTS13:AC resulting in formation of an ADAMTS13:INH, and therapeutic plasma exchange is necessary for treatment. Disclosures: Ortel: Eisai: Research Funding; Glaxo SmithKline: Research Funding; Pfizer: Research Funding; Instrumentation Laboratory, Inc: Consultancy, Research Funding; Boehringer Ingelheim: Consultancy. Fujimura:Baxter BioScience: Membership on an entity's Board of Directors or advisory committees; Alexion Pharma: Membership on an entity's Board of Directors or advisory committees.