Clinical correlates of HLA-B*27 and its subtypes in enthesitis-related arthritis variant of juvenile idiopathic arthritis in south Indian Tamil patients.

Aim: The aim of the study was to assess the distribution of human leukocyte antigen (HLA)-B*27 subtypes and its correlation with disease phenotypes in children with enthesitis-related arthritis variant of juvenile idiopathic arthritis (JIA-ERA).

Method: One hundred and sixty patients (132 males, 28 females) satisfying the International League Against Rheumatism (ILAR) classification criteria for JIA-ERA were assessed and relevant demographic, clinical and radiographic data were documented. HLA-B*27 typing was done for all the patients and B*27 positive samples were subjected to high-resolution gene sequencing. The effect of duration of illness, HLA-B*27, its subtypes, and gender on the clinical phenotype were analyzed.

Results: The mean age of disease onset was 12.69 ± 2.4 years with a male:female ratio of 4.7:1.0. HLA-B*27 was positive in 109/160 patients and HLA-B*27:04 was detected in 63% followed by B*27:05 (30%). Duration of illness was greater in patients with skeletal deformity, hip arthritis, sacroiliitis, cervical spine involvement and acute anterior uveitis (AAU) (P < 0.05). HLA-B*27 positivity was associated with a prolonged course of disease, higher incidence of AAU (14.7% vs 2%, P = 0.015), family history of spondyloarthritis (21.1% vs 5.9%; P = 0.015) and higher erythrocyte sedimentation rate as compared to HLA-B*27 negative patients (P < 0.01). The HLA-B*27:04 and *27:05 positive patients had similar clinical phenotypes.

Conclusion: Presence of HLA-B*27 and long duration of illness results in skeletal deformity, hip arthritis, sacroiliitis, cervical spine involvement and AAU. HLA-B*27:04 followed by B*27:05 are the most common HLA-B*27 subtypes in our study population and both have a similar clinical phenotype.