Tumor necrosis factor receptor II and PTPN22 genes polymorphisms and the risk of systemic lupus erythematosus in Egyptian children

Abstract

Background: Many genes have been implicated in the pathogenesis of systemic lupus erythematosus (SLE). Tumor necrosis factor (TNF) is a potent cytokine stimulator acting through 2 cell surface receptors (TNFR I and II). TNFRII gene which controls expression of these receptors has been linked to SLE susceptibility through promoting apoptosis. Also; Protein tyrosine phosphatase non receptor 22 (PTPN22) gene enhances intrinsic phosphatase activity of T lymphocytes leading to their dysregulation and stimulates autoimmune process of lupus and its rs2476601 has been linked to susceptibility to thyroiditis in SLE patients in few studies.

Objectives: (i) to investigate the correlation between 2 SNPs of TNFR II and PTPN22 genes and SLE susceptibility in a cohort of Egyptian children compared to controls (ii) and to investigate their possible association with different clinical presentations of the disease in children.

Subjects and methods: Typing of TNFR II rs1061622 and PTPN22 rs2476601 SNPs were done using polymerase chain reaction-restriction fragment length polymorphism for 74 children with SLE and 100 matched healthy controls.

Results: Children with SLE had more frequent G allele and GG genotype of TNFR II rs1061622 (p < 0.001) and more T allele and TT genotype of PTPN22 rs2476601 (p = 0.012 and <0.001, respectively) compared to controls. Only 6 patients (8%) had thyroiditis (hypothyroidism) with T allele and TT genotype of PTPN22 1858 T more prevalent in those patients versus those without thyroiditis (p ≤ 0.001). Apart from, thyroiditis, no significant association was found between genotypes and alleles frequencies of the 2 studied SNPs and other clinical manifestations of the disease.

Conclusion: The G allele and GG genotype of TNFR II rs1061622 and T allele and TT genotype of PTPN22 rs2476601 genes polymorphism can be considered as risk factors for the development of SLE. The presence of the T allele of PTPN22 rs2476601 may increase the risk of concomitant thyroiditis in Egyptian children with SLE but further studies are required to confirm this finding as thyroiditis was reported only in few cases in this study.

Keywords: Egyptian children; PTPN22; Tumor necrosis factor receptor II; systemic lupus erythematosus.