Association of ERAP1, IL23R and PTGER4 Polymorphisms with Radiographic Severity of Ankylosing Spondylitis

Radiographic severity of ankylosing spondylitis (AS) shows such great variance that some patients never develop syndesmophytes throughout the entire disease span, whereas some develop bamboo spine relatively early.

To study the association between ERAP1, IL23R and PTGER4 single nucleotide polymorphisms (SNPs) and radiographic severity in AS patients.

rs27044 and rs30187 (ERAP1), rs11209032 (IL23R) and rs10440635 (PTGER4) SNPs were genotyped in 235 AS patients fulfilling the modified New York criteria. Patients were classified as mild- and severe-AS according to modified Stoke AS spinal score (mSASSS). Mild-AS is defined as having mSASSS of “0” following at least 10 years of disease duration. Severe-AS is defined as having mSASSS of >20 (patients with mild vertebral changes (i.e. squaring or erosions) were omitted for clear stratification) regardless of disease duration.

The genotype distributions and allele frequencies of ERAP1 rs27044 and rs30187, IL23R rs11209032 and PTGER4 rs10440635 SNPs were similar in mild- (n=171, mSASSS=0, 55.6% HLA-B27 positive) and severe-AS patients (n=64, mSASSS=48.5±17.8, 73.4% HLA-B27 positive). After adjustment for clinical differences between groups (gender, disease duration, HLA-B27 and smoking status) by logistic regression analysis, none of the alleles in the investigated SNPs were found to be associated with radiographic severity of AS.

In radiographically well-categorized AS patients, ERAP1 rs27044 and rs30187, IL23R rs11209032 and PTGER4 rs10440635 SNPs are not found to be associated with radiographic severity of AS.