Analysis of 6 genetic loci for disease susceptibility in psoriatic arthritis

To analyze the association of several autoimmune disease susceptibility loci in a population of patients with psoriasis and defined joint disease from northern Sweden.

One hundred twenty patients with psoriasis and defined joint disease were examined clinically, radiologically, and with laboratory-based analyses. Disease classification was based on peripheral and/or axial engagement. The tumor necrosis factor (TNF) locus, 1q21 (PSORS4), 3q21 (PSORS5), 8q24, 16q21, and the CTLA4 gene were analyzed using a total of 38 microsatellite markers and 2 single nucleotide polymorphisms (SNP). Ninety-four controls with the same ethnic background as the patients were randomly selected from the same region of Sweden.

An association was found with one of the markers in the TNFB locus within the HLA region (p = 0.012, pc = 0.024). Three markers at the PSORS4 locus on chromosome 1q21 and 2 markers at the 8q24 locus showed nominal p values of < 0.05. After applying the Bonferroni correction for multiple analyses these markers did not reach significance. No other marker showed significant association. In a subgroup of the patients, possible linkage disequilibrium between the TNFB123 and HLA-B antigens, B17, B27, B37, B44, and B62 was analyzed. A significant linkage (p = 0.0001) was found.

We identified an association between psoriatic arthritis and one of the microsatellite markers within the TNFB locus at the HLA region on chromosome 6. Linkage disequilibrium between TNFB123 and certain HLA-B antigens was found.