R620W polymorphism of protein tyrosine phosphatase PTPN22 in Egyptian children and adolescents with systemic lupus erythematosus: relation to thyroid autoimmunity

Abstract

Some studies showed associations of the minor T allele of the C1858T single nucleotide polymorphism (SNP) corresponding to the R620W amino acid substitution of protein tyrosine phosphatase (PTPN22) with multiple autoimmune diseases, including systemic lupus erythematosus (SLE). To study the frequency of PTPN22 R620W polymorphism among Egyptian patients with SLE and to test the association of the T allele with autoimmune thyroid disease in such patients. Clinical evaluation, measurement of thyroid hormones and antibodies, and genotyping of PTPN22 R620W polymorphism were done for 60 SLE patients and 60 age- and sex-matched healthy subjects. Nineteen SLE cases (31.67%) had thyroid dysfunction with subclinical hypothyroidism being the most frequent form of thyroid dysfunction (20%) followed by primary hypothyroidism (6.67%), subclinical hyperthyroidism (3.33%) and primary hyperthyroidism (1.67%). Autoimmune thyroid disease was detected in 36.67% of cases. Systemic lupus erythematosus disease activity index (SLEDAI) score did not differ between patients with thyroid dysfunction and euthyroid patients (p=0.061) nor with the frequency of positive thyroid peroxidise antibodies (TPOAb, p=0.092) and antithyroglobulin antibodies (ATGAb, p=0.1). T allele frequency did not differ between cases and controls (p=1.19) and was associated with autoimmune thyroid disease in Egyptian SLE patients (p=0.002). R620W polymorphism of the PTPN22 gene is not a major risk allele for SLE susceptibility among Egyptian SLE patients but appears to be a risk factor for concurrent autoimmune thyroid disease and SLE.