PB1334 - Immune-mediated Thrombotic Thrombocytopenic Purpura (iTTP): Single Centre Experience

Background: iTTP is a rare disorder with an incidence of 2 to 6 per million individuals and is associated with a high mortality rate (>90%) if not treated. The disease results from autoantibody-mediated severe deficiency of ADAMTS13. Patients present with thrombocytopenia, microangiopathic hemolytic anaemia and various degrees of organ damage. Immunosuppression and Therapeutic Plasma Exchange (TPE) are used as preferred treatments, along with caplacizumab, an anti-vWF nanobody.

Aims: In our patients with iTTP, the main goal was to determine the time to clinical response since the first TPE. Moreover, we evaluated the number of exacerbations, relapses, TPE sessions needed for clinical response, percentage of clinical remission and mortality rate.

Methods: Data was collected from iTTP patients’ clinical records covering the past ten years (2015-2024).

Results: We followed six patients (n=5 patients, no caplacizumab treatment, n=1 patient with caplacizumab treatment) with an average age of 49 years, mainly women (n=4, 66,7%) at our institution.
In the group of patients not treated with caplacizumab, the median time to clinical response was 8 (IQR, 6-32) days. Patients achieved clinical response after a median of 8 (IQR 6,5-61,5) TPE sessions. Two patients presented with exacerbations and one was refractory. All these patients achieved clinical remission.
Administration of caplacizumab occurred in just one patient (December 2023), as frontline therapy, on the 3rd TPE session. The patient achieved clinical response in 12 days after a total number of 9 TPE sessions. There were no exacerbations and refractoriness. There were no adverse events with the use of caplacizumab.
All patients are still being followed at our institution, there were no relapses documented. None of the n=6 patients died.

Conclusion(s): To summarize, none of our patients relapsed. Our results are in line with previous studies.
In the future, we need to insert our patients in a multicenter study to draw significant conclusions.