Interleukin 1alpha, interleukin 1beta and interleukin 1 receptor gene polymorphisms in psoriatic arthritis.

OBJECTIVES

To investigate polymorphisms of interleukin (IL) 1alpha, IL-1beta and IL-1 receptor R1 genes in patients with psoriatic arthritis (PsA), their relationship to the age of onset of psoriasis and the pattern of joint involvement.

METHODS

One hundred and forty well-characterized patients with PsA were studied. One hundred healthy controls were recruited from primary care. All were genotyped for single-nucleotide polymorphisms in the genes for IL-1alpha (position -889), IL-1beta (position +3953) and IL-1R1 (position +970). The frequencies of the respective variants were compared between patients and controls and in relation to age of onset of psoriasis, to clinical subsets of the disease and to the presence of erosions.

RESULTS

All three polymorphisms were in Hardy-Weinberg equilibrium in both patients and controls. The frequency of IL-1alpha -889 CC homozygotes was significantly increased in PsA patients compared with normal controls [58 vs 40%, odds ratio (OR) 2.06, 95%, confidence interval (CI) 1.22-3.47]. The frequency of the IL-1alpha -889 C allele was significantly increased in PsA patients compared with controls (75 vs 65%, OR 1.65, 95% CI 1.11-2.45). In subset analysis there were no other significant differences in allelic frequencies for the IL-1alpha -889 C/T, IL-1beta +3953 C/T and IL-1R1 +970 C/T polymorphisms.

CONCLUSIONS

The IL-1 gene complex may play a role in the development of PsA and/or psoriasis or act as a marker for other genes on chromosome 2q12 to 2q13.