Association of a PDCD1 polymorphism with renal manifestations in systemic lupus erythematosus

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Abstract
Objective To analyze the association of the PD-1.3 polymorphism within the PDCD1 gene in patients with systemic lupus erythematosus (SLE) from the homogeneous population in northern Sweden. The PD-1.3A allele was analyzed in relation to disease manifestations and severity representing various phenotypes of SLE. Methods The study group comprised 260 patients fulfilling at least 4 of the American College of Rheumatology (ACR) criteria for SLE during 1 year. The Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) and the Systemic Lupus International Collaborating Clinics/ACR damage index scores were recorded. Population-based, randomly selected individuals (n = 670) from the same geographic area served as controls. DNA was extracted from blood samples from both patients and controls and was genotyped for the PD-1.3 A/G polymorphism, using an ABI Prism 7900HT Sequence Detection System. Results The frequency distribution of alleles, carriers, or genotypes did not differ between patients and controls. The PD-1.3A allele and carriage of the A allele were highly associated with renal disorder (ACR criterion 7) (P = 0.005, odds ratio [OR] 2.71 [95% confidence interval (95% CI) 1.32–5.55] and P = 0.012, OR 2.62 [95% CI 1.28–5.35], respectively). In regression analysis adjusted for sex and age at disease onset, carriage of the A allele remained significantly associated with renal disorder (P = 0.002, OR 3.54 [95% CI 1.56–8.01]). The presence of proteinuria, as measured by the SLEDAI score, and the presence of renal damage were also significantly associated with carriage of the A allele (P = 0.007, OR 3.88 [95% CI 1.44–10.47] and P = 0.021, OR 2.98 [95% CI 1.18–7.54], respectively). Conclusion The PD-1.3A allele is associated with renal manifestations in SLE patients from northern Sweden but not with susceptibility to SLE per se.