Clinico-immunological profile of seronegative axial spondyloarthritis with special emphasis on the role of human leukocyte antigen B27

Objectives Human leukocyte antigen B27 (HLA-B27) is an allele of the major histocompatibility complex Class I molecules and is considered a causative genetic factor in seronegative spondyloarthritis. Seronegative spondyloarthritis (SpA) is a group of immune-mediated arthritis involving but not confined to the axial skeleton. The entities have overlapping yet different presentations. To understand the phenotypic implications of the B27 genotype in the disease process, we have compared the phenotype of HLA-B27 positive (H+) versus HLA-B27 negative (H−) spondyloarthritis patients. Materials and Methods A retrospective observational study including 218 patients with features of axial SpA was included in the study. Polymerase chain reaction-sequence-specific primer method was performed for the genotyping of B27. Statistical analysis Two groups of H+ and H− patients were compared using the Chi-square test. Results 116 H+ and 102 H− patients with features of spondyloarthritis were analyzed. Younger age, sacroiliitis, multiple joint pain, morning stiffness, uveitis, and higher disease activity (raised C-reactive protein) were significantly associated with H+ compared to H− groups. Family history of SpA and related features was present in both groups, but it was slightly more common in H+ than H−. Conclusions The present study is one of the very few Indian studies elaborating on the impact of H+ genotype in the phenotype of axial seronegative SpA. HLA-B27 has a causative genetic association with seronegative SpA. However, H− patients also had a positive family history in 35% of patients in the present study, thus pointing toward other genetic associations apart from HLA B 27.