Seronegative spondyloarthropathies and HLA-B27 subtyes: a study in Asian Indians

In this study, 60 HLA-B27+ve SSA patients and 17 healthy controls belonging to North India were analyzed to ascertain heterogeneity of the B27 molecule in this population. ID-IEF and PCR-SSOP technologies were used to analyze polymorphism in exon 2 and 3 of the HLA-B27 gene. Four different subtypes were encountered: B*2702,04,05 and 07. Other subtypes of B27 viz B*2701,03,06 and 08 were not encountered. B*2704 (common oriental subtype) and B*2705 (common Caucasian subtype) were the most common subtypes in the control and patient groups. B*2707 was less frequently encountered in both groups and B*2702 was found in only one AAU patient. B*2704 was the predominant subtype in the AS group (70.8%) compared to its frequency of 47% in healthy controls (RR = 2.73) while in the undiff SpA group, B*2705 occurred most frequently (73.1%, RR = 3.05). B27 subtypes segregated differently in males and females. 12 of the 17 male AS patients carried B*2704 as compared to 1 of 8 healthy males (X2 = 3.9, P < 0.05). On the other hand, in the undiff SpA, B*2705 was significantly raised in female patients (100%) as compared to healthy females (22.2%, X2 = 4.9, P < 0.05). Subtype distribution is indicative of racial admixture in the Asian Indian population.