Background/Purpose: HLA-B27 has a high degree of genetic polymorphism, with more than 105 known subtypes. Enthesitis Related Arthritis (ERA) is most common form of Juvenile Idiopathic Arthritis (JIA) in Asian and Indian population. It has strong association with HLA B27 similar to the adult ankylosing spondylitis (AS). Since the disease occurs in children and different HLA B27 subtypes confer different susceptibility to AS we studied the HLA-B27 subtypes associated with ERA and AS to see if there is any difference.

Methods: Samples were collected from 135 patients with ERA and 121 patients with AS. Genomic DNA was isolated from whole blood using salting out technique and HLA B27 typing was done using ARMS-PCR. Primers for intronic region of HLA-DR were used as internal control. HLA-B27 subtyping was done by sequencing using a group-specific amplification of the second and third exon region of HLA B27 gene.

Results: Hundred and seven out of 135 patients with ERA (79%) and 102/121 (84%) of AS patients were HLA B27 positive. HLA B*2705 and 04 were the most common subtypes. HLA B2*27:02, 07 and 018 were seen rarely. The frequency of HLAB*27:05 was 70% in ERA as compared to 56.8% in AS (p=0.032) whereas HLAB*27:04 was 21.4% in ERA and 36.2% in AS (p=0.013). No correlation was seen between B*27 subtypes (B*2704 and B*2705) and clinical features of JIA-ERA.

Conclusion: HLAB*27 subtype frequencies are different in ERA and AS. It is possible that the presence of ancestral subtype HLA B*27:05 leads to early onset of disease.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/hla-b27-subtypes-in-enthesitis-related-arthritis-category-of-juvenile-idiopathic-arthritis/