Arthritis & Rheumatism, Volume 62,
November 2010 Abstract Supplement

Abstracts of the American College of
Rheumatology/Association of Rheumatology Health Professionals
Annual Scientific Meeting
Atlanta, Georgia November 6-11, 2010.


Subtype Specific Genetic Associations for Juvenile Idiopathic Arthritis (JIA): ERAP1 with the Enthesitis Related Arthritis Subtype and IL23R with Juvenile Psoriatic Arthritis.

Hinks1,  Anne, Martin2,  Paul, Flynn2,  Edward, Eyre2,  Steve, Packham3,  Jon, Barton2,  Anne, Worthington2,  Jane

Arthritis Research UK Epidemiology Unit, University of Manchester, Manchester, United Kingdom
Arthritis Research UK Epidemiology Unit, University of Manchester
Haywood Hospital, University Hospital of North Staffordshire

Background:

There is now strong evidence supporting the hypothesis of common autoimmune susceptibility loci. There is also evidence to support clustering of loci in diseases that share similar clinical phenotypes e.g. Ankylosing spondylitis (AS), psoriasis (Ps), psoriatic arthritis (PsA) and they appear to have some overlapping susceptibility loci such as IL23R and ERAP1.

Juvenile idiopathic arthritis (JIA) is an umbrella term for all chronic childhood arthropathies and can be classified into 7 subtypes on the basis of features present in the first 6 months of disease. It includes the enthesitis related arthritis (ERA) subtype which displays symptoms similar to AS and juvenile onset psoriatic arthritis which has similarities to psoriatic arthritis and psoriasis. We therefore hypothesized that the two well-established susceptibility loci IL23R and ERAP1 could also confer susceptibility to these JIA subtypes, to this end the most associated SNP within each of these genes have been selected for genotyping across all JIA and also analysed stratified for each subtype.

Methods:

SNPs in IL23R (rs1129026) and ERAP1 (rs30187) were genotyped in JIA cases (n=1054) and healthy controls (n=5200). The numbers genotyped per ILAR subgroup were: Systemic onset (n=164), persistent oligoarthritis (n=297), extended oligoarthritis (n=147), Rheumatoid factor (RF) negative polyarticular JIA (n=215), RF positive polyarticular JIA (n=68), enthesitis related JIA (n=63), psoriatic JIA (n=76) and unclassified (n=24).Genotype and allele frequencies were compared between all JIA cases and controls using the Cochrane-Armitage trend test implemented in PLINK and allelic odds ratios (ORs) and their 95% confidence intervals (CIs) calculated. Stratified analysis by subtype was performed.

Results:

Neither the SNP in the IL23R gene, rs1129026, nor the SNP in the ERAP1 gene, rs30187, were significantly associated (p<0.05) with the total JIA dataset. Stratification by subtype found that the IL23R SNP showed significant association in the psoriatic arthritis subtype (ptrend=0.04 OR 0.4 95% CI 0.16–0.98) and a trend towards association in the enthesitis related subtype (ptrend=0.15 OR 0.52 95% CI 0.21–1.28). The enthesitis related arthritis (ERA) subtype showed strong association with ERAP1 SNP (ptrend=0.004 OR 1.69 95% CI 1.18–2.44). For both SNPs the association is in the same direction as in the original study.

Conclusions:

We present evidence for subtype specific association of the IL23R gene with juvenile psoriatic arthritis and ERAP1 gene with ERA. The findings will require validation in independent JIA datasets. These results suggest distinct pathogenic pathways in these subtypes.

Acknowledgements:

Childhood arthritis prospective study (CAPS) and BSPAR study group

To cite this abstract, please use the following information:
Hinks, Anne, Martin, Paul, Flynn, Edward, Eyre, Steve, Packham, Jon, Barton, Anne, et al; Subtype Specific Genetic Associations for Juvenile Idiopathic Arthritis (JIA): ERAP1 with the Enthesitis Related Arthritis Subtype and IL23R with Juvenile Psoriatic Arthritis. [abstract]. Arthritis Rheum 2010;62 Suppl 10 :266
DOI: 10.1002/art.28035

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