PB0313 - A cohort study of 22 patients with immune-mediated thrombotic thrombocytopenic purpura in Taiwan

Background: Immune-mediated thrombotic thrombocytopenia purpura (iTTP) is caused by the development of auto-antibodies with severely decreased activity of the von Willebrand factor-cleaving protease, ADAMTS13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13).

Aims: To reported a cohort of 22 patients with iTTP in Taiwan.

Methods: Between 2012 and 2023, 22 patients with iTTP diagnosed in the Changhua Christian Hospital were enrolled. The clinical features, laboratory results, therapeutic plasma exchange (TPE) data, and clinical outcomes were collected.

Results: All presented with microangiopathic hemolytic anemia (MAHA) with thrombocytopenia (22), whereas schistocytes (21), neurologic deficits (16), renal impairment (17), fever (14), and elevated cardiac troponin-I (11) were observed. In patients with available samples before treatment, we confirmed that a severe deficiency (i.e., less than 10%) of ADAMTS13 activity was caused by high-titered autoantibody.
All patients received TPE (5 to 90 sessions). Most (19/22) also had upfront glucocorticoid. Six received rituximab in rescue. A complete clinical response was achieved in 18 patients (81.8%). Cases of exacerbation, relapse and mortality were also observed.

Conclusion(s): In our cohort, MAHA with schistocytes and thrombocytopenia are the laboratory hallmarks for diagnosis, in addition to low activities of ADAMTS13. Despite a high response rate was revealed, the complications observed also indicated substantial unmet therapeutic needs in Taiwan.