Immune-mediated thrombotic thrombocytopenic purpura (iTTP) are characterized by recurrent thrombotic microangiopathy events that impair ischemic organ function. Black patients make up a disproportionate amount of iTTP cohorts in the US. However, research on racial differences in iTTP outcomes and the therapeutic response was lacking.

Utilizing data from the United States Thrombotic Microangiopathies Consortium iTTP Registry, researchers assessed the effect of race on mortality and relapse-free survival (RFS) in confirmed cases of iTTP in the country from 1995 to 2020. They separately looked at how rituximab treatment and the presence of freshly diagnosed (de novo) or relapsed iTTP affected RFS by race. There were 645 participants in all, and there were 1,308 iTTP sessions available for study. The race did not affect acute iTTP mortality. When all bouts of iTTP were included, the Black race was linked to a shorter RFS (hazard ratio [HR], 1.60; 95% CI, 1.16-2.21). However, black patients did not benefit from adding rituximab to corticosteroids. Rituximab delayed relapse in de novo iTTP, Black patients’ RFS (HR, 0.96; 95% CI, 0.71-1.31) was shorter than White patients’ (HR, 0.37; 95% CI, 0.18-0.73) independent of therapy. Rituximab substantially increased RFS in White but not Black individuals with relapsed iTTP.

Overall, recurrence risk and rituximab response in iTTP were influenced by race. Following rituximab therapy, black individuals may need more frequent monitoring, earlier retreatment, and different immunosuppression. It was important to continue researching the differences in relapse risk in iTTP and how race, racism, and socioeconomic determinants of health affected them.