Effect of Blood Groups on Clinical Presentations and Treatment Outcomes in Immune Thrombotic Thrombocytopenic Purpura Patients with Severe ADAMTS13 Deficiency: A Multi-Center Experience.

Introduction: Thrombotic thrombocytopenic purpura (TTP) is a thrombotic microangiopathy caused by accumulation of ultra-large von Willebrand factor (vWF) due to the significantly reduced activity ADAMTS13. Limited studies have been published examining the blood group as an epidemiological factor that can contribute to development of TTP. It has been suggested that due to low vWF levels, the distribution of the "O" blood group among TTP patients may be lower than anticipated compared to the blood group distribution rates in the normal population. The aim of this study was to explore the relationship between blood groups and the clinical outcome of immune TTP (iTTP). Methods: Thirty patients with iTTP with severe ADAMTS13 deficiency were enrolled. Data collection commenced in January 2011 and was completed by June 2020. It was analyzed whether there was a difference between the blood groups in terms of frequency of iTTP, response to treatment, frequency of relapse, and clinical and laboratory results. Results and Conclusions: The distribution of group "A" among patients with iTTP was higher than expected. Although not statistically significant, patients with blood group "O" required more TPE for the treatment and relapse rate was statistically higher than other blood groups. Mortality rate in all patients was 6.7%. Although blood group "A" is a risk factor for iTTP, the frequency of relapse is higher in the blood group "O."