Evaluating the impact of the ABO blood group on the clinical outcome of thrombotic thrombocytopenic purpura associated with severe ADAMTS13 deficiency.

BACKGROUND AND OBJECTIVES

Thrombotic thrombocytopenic purpura (TTP) is caused by the decrease of ADAMTS13, leading to the accumulation of ultra large von Willebrand factor (ULVWF). It was proposed that the distribution of blood group O among TTP patients may be potentially lower than expected because of the lower levels of VWF. The aim of this study was to explore the relationship between various blood groups and the clinical outcome in TTP.

MATERIALS AND METHODS

Thirty-three patients with TTP with severe ADAMTS13 deficiency were studied. Data on blood group, relapse, number of plasma exchange sessions, replacement fluid and mortality were analysed.

RESULTS

Mortality rate was 15·2% and it was not impacted by blood group. The distribution of group O among patients with idiopathic TTP was lower (12%) than expected (30%). Patients with blood group O required more sessions to achieve remission than did those with group B (P = 0·02). Cryo-supernatant was used in three refractory patients with group O, who failed to respond to fresh-frozen plasma and complete remission was achieved. The overall number of relapsing episodes was 7 of 33 (21·2%), and it was not impacted by blood group.

CONCLUSION

Although blood group O appeared to provide protection against TTP, more sessions were required to achieve remission. Cryo-supernatant improved the clinical outcome in refractory patients with group O. Future studies may be warranted to determine whether higher baseline VWF can be a trigger for TTP, or can confer protection by competing with a newly secreted ULVWF for platelet binding.