Background/Purpose: PSA is a chronic inflammatory disease associated to psoriasis which affects the joints, vertebrae and enthesis. Interleukin-1 is an inflammatory cytokine. A higher expression of IL-1 has been observed in the synovial fluid of patients with PSA. Interleukin-6 promotes synovitis and enhances bone resorption. No studies have analyzed the relation between PSA patients with polymorphisms of IL-1β (-511 A/C) and IL-6 (-174 G/C) and the activity, the presence of erosions or the clinical form of presentation. We relate the polymorphisms of IL-1β (-511 G/A) and IL-6 (-174 G/C) with inflammatory activity, radiographic damage and clinical forms in a group of PSA patients. 

Methods: We studied 125 patients diagnosed with PSA according to the CASPAR criteria. The patients were classified depending on whether they presented peripheral, axial or mixed. The activity in the peripheral or mixed forms was measured according to the number of swollen, painful joints, visual analogue scale, ESR and CRP. The DAS 28 index was calculated. For the axial and mixed forms, the BASDAI index, the visual analogue scale, ESR and CRP were used. In the assessment of radiographic damage we used the SvH and mSASSS. All patients underwent an analysis of the polymorphism in the promoter region of IL-1β (-511 G/A) and IL-6 (-174 G/C). 

Results: 59.2% of the patients were men. 13 patients showed axial involvement (10.4%), 38 a mixed involvement (30.4%), and 74 a peripheral involvement (59.2%). The distribution and genotype of the polymorphism of IL-1β (-511 G/A), with regard to the number of swollen joints and DAS>3.2 are included in Table 1. In the logistic regression model: DAS>3.2 (p=0.018; OR: 3.46). In the allele analysis, 30.92% of the carriers of the G allele showed DAS over 3.2, compared with 12.5% of the patients with the A allele (OR: 3.13); p<0.0004; 95% CI: 1.43-6.82; adjusted p<0.008). No differences were found regarding the distribution of the polymorphism in the different clinical forms of the disease or the radiographic damage. With regard to the polymorphism of IL-6 (-174 G/C) in the group of G/G homozygous patients, compared with the combined group of G/A and A/A patients, we found differences in the clinical forms of PSA and in the frequency of appearance of HLA-B27 antigen (Table 1). In the logistic regression analysis: types of disease (p=0.007; OR=2.741) and HLA-B27 (p=0.001; OR=0.103). The G allele was not more frequently found in peripheral forms (70.86%) than in mixed forms (57.42%) (OR=1.89; p<0.03; 95% CI: 1.06-3.39; adjusted p<0.05). We did find a lower association of the G allele with HLA-B27 (15.78%) compared with the C allele (28.57%) (OR= 0.469; p=0.02; 95% CI: 0.238-0.923; adjusted p<0.03). 

Conclusion: The G allele of polymorphism IL-1β (-511 A/C) was associated with the presence of more inflammatory activity. We found a trend in patients who carried the G allele of the polymorphism IL-6 (-174 G/C) to present with a peripheral form of the disease.

Tabla1.

	IL1ß (-511 A/C)	Mean (SD)			p
NSJ	G/G	2.09 (1.99)			0.03
	G/A	1.49(1.56)
	A/A	1.45(1.50)
DAS>3.2		Yes		No	0.005
	G/G	20		31
	G/A	7		43
	A/A	1		10
	IL6 (- 174 G/C)	Patients
AXIAL	G/G	6			0.009
	G/C+C/C	7
PERIPHERAL	G/G	39
	G/C+C/C	35
MIXED	G/G	10
	G/C+C/C	28
HLAB27		POSITIVE	NEGATIVE		0.003
	G/G	3	46
	G/C+C/C	19	43

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/influence-of-the-polymorphism-il1s-511-ac-and-il6-174-gc-on-the-activity-radiographic-damage-and-clinical-forms-of-patients-with-psoriatic-arthritis-psa/