Increased frequency of HLA-B7 among B27-negative seronegative spondarthritis patients from Mumbai, western India.

Seronegative spondarthritis (SSA) is a group of inflammatory disorders that shares certain clinical features and has a strong association with the human leucocyte antigen (HLA)-B27 allele. Serologically, HLA-B27, HLA-B22, HLA-B7, HLA-B40 and HLA-B42 antigens belong to the HLA-B cross-reacting antigen group (CREG). In addition to B27, other B locus antigens are associated with B27-negative American black, Brazilian, French and Chinese SSA patients. Many B27-negative individuals in India have developed SSA with severe clinical and radiological findings. This stimulated the evaluation of the involvement of HLA-B7 CREG antigens among B27-negative SSA patients from western India. A total of 276 SSA patients who were B27-negative and fitted the modified New York criteria for AS and the European Spondyloarthropathy Study Group (ESSG) criteria for spondarthritis from western India were studied and compared with 637 normal, healthy individuals who were B27-negative and of the same ethnic background. A significantly increased phenotype frequency of HLA-B7 (PF = 57.24% vs. 22.44%; P < 0.001) and a significant decreased phenotype frequency of HLA-B40 (PF = 18.11% vs. 31.86%; P < 0.001) was observed when compared to the controls. These results suggest that HLA-B7 antigen may be associated with B27-negative SSA in patients from western India.