Thrombotic Thrombocytopenic Purpura in Black People: Impact of Ethnicity on Survival and Genetic Risk Factors

PLoS One. 2016 Jul 6;11(7):e0156679. doi: 10.1371/journal.pone.0156679. eCollection 2016.


Black people are at increased risk of thrombotic thrombocytopenic purpura (TTP). Whether clinical presentation of TTP in Black patients has specific features is unknown. We assessed here differences in TTP presentation and outcome between Black and White patients. Clinical presentation was comparable between both ethnic groups. However, prognosis differed with a lower death rate in Black patients than in White patients (2.7% versus 11.6%, respectively, P = .04). Ethnicity, increasing age and neurologic involvement were retained as risk factors for death in a multivariable model (P < .05 all). Sixty-day overall survival estimated by the Kaplan-Meier curves and compared with the Log-Rank test confirmed that Black patients had a better survival than White patients (P = .03). Salvage therapies were similarly performed between both groups, suggesting that disease severity was comparable. The comparison of HLA-DRB1*11, -DRB1*04 and -DQB1*03 allele frequencies between Black patients and healthy Black individuals revealed no significant difference. However, the protective allele against TTP, HLA-DRB1*04, was dramatically decreased in Black individuals in comparison with White individuals. Black people with TTP may have a better survival than White patients despite a comparable disease severity. A low natural frequency of HLA-DRB1*04 in Black ethnicity may account for the greater risk of TTP in this population.

MeSH terms

  • Adult
  • Alleles
  • Black People / genetics*
  • Black or African American / genetics*
  • Female
  • Gene Frequency
  • HLA-DQ beta-Chains / genetics
  • HLA-DRB1 Chains / genetics
  • Humans
  • Kaplan-Meier Estimate
  • Male
  • Middle Aged
  • Purpura, Thrombotic Thrombocytopenic / ethnology*
  • Purpura, Thrombotic Thrombocytopenic / genetics*
  • Purpura, Thrombotic Thrombocytopenic / mortality
  • Registries
  • Risk Factors
  • Treatment Outcome
  • White People / genetics


  • HLA-DQ beta-Chains
  • HLA-DQB1 antigen
  • HLA-DRB1 Chains
  • HLA-DRB1*04 antigen
  • HLA-DRB1*11 antigen

Grants and funding

The authors have no support or funding to report.