Association of HLA-B*41:02 with Henoch-Schonlein Purpura (IgA Vasculitis) in Spanish individuals irrespective of the HLA-DRB1 status

Introduction: A study was conducted to determine whether the human leukocyte antigen (HLA) B alleles are implicated in the susceptibility to Henoch-Schonlein purpura (HSP) in the largest series of Caucasian HSP patients ever assessed for genetic studies. Methods: The study population was composed of 349 Spanish patients diagnosed with HSP fulfilling the American College of Rheumatology and the Michel et al. classification criteria, and 335 sex and ethnically matched controls. HLA-B phenotypes were determined by sequencing-based typing (SBT) and analyzed by chi-square or Fisher exact test. Results: A statistically significant increase of HLA-B*41:02 allele in HSP patients when compared with controls was found (8.3% versus 1.5% respectively; P = 0.0001; OR (odds ratio) = 5.76 [2.15-19.3]). These results remained statistically significant after adjusting for Bonferroni correction (P = 0.0028). An internal validation also confirmed the susceptibility effect on HSP associated with HLA-B*41:02 (OR = 5.70 [1.98-16.44]). Since a former study described an association between HLA-DRB1*01:03 and HSP susceptibility, we also evaluated the implication of HLA-B*41:02 independently of HLA-DRB1*01:03. Interestingly, the association remained statistically significant (P = 0.0004, OR = 4.97 [1.8-16.9]). No HLA-B association with specific HSP clinical features was found. Conclusions: Our study indicates that HLA-B*41:02 is associated with the susceptibility to HSP in Spanish patients irrespective of HLA-DRB1 status.