title: The R620W polymorphism of the protein tyrosine phosphatase 22 gene in autoimmune thyroid diseases and rheumatoid arthritis in the Tunisian population.
abstract: BACKGROUND
  Protein tyrosine phosphatase (PTPN22) is involved in the negative regulation of T-cell responsiveness. The association of a coding variant of the PTPN22 gene (R620W) with a number of autoimmune diseases has been described.
  
  
  OBJECTIVE
  The present study investigated whether PTPN22 gene polymorphism was also involved in the genetic predisposition to autoimmune thyroid diseases (AITDs) and rheumatoid arthritis (RA) in a Tunisian case control study.
  
  
  METHODS
  DNA samples from 150 patients affected with RA, 204 patients affected with AITDs and 236 healthy controls were genotyped for PTPN22 R620W polymorphism (1858C/T). Genotyping was performed by the polymerase chain reaction-restriction fragment length polymorphism method.
  
  
  RESULTS
  No significant differences in T allele frequency (2.3% in RA patients and 1% in AITDs patients vs 2.6% in controls; p=0.85 and p=0.08, respectively) and in genotype frequencies were detected between RA patients and controls (p=0.15) and between AITDs patients (p=0.11). Stratifying patients affected with AITDs according to their phenotype (Graves' disease and Hashimoto's thyroiditis) and RA patients according to the presence of rheumatoid factor (RF) and antibodies against cyclic citrullinated peptides (ACPA) did not show any significant association with PTPN22 R620W allele (p>0.05).
  
  
  CONCLUSIONS
  Our data suggest that the PTPN22 C1858T single nucleotide polymorphism has no or minor effect on RA and AITDs susceptibility in the Tunisian population.
authors.affiliation: Faculté de Médecine de Sfax, Laboratoire de Génétique Moléculaire Humaine, Sfax, Tunisia. ghazi.chabchoub@laposte.net
authors.forename: Ghazi
authors.initials: G
authors.lastname: Chabchoub
authors.forename: Elisabeth Petit
authors.initials: EP
authors.lastname: Teixiera
authors.forename: Abdellatif
authors.initials: A
authors.lastname: Maalej
authors.forename: Mariem
authors.initials: M
authors.lastname: Ben Hamad
authors.forename: Zouheir
authors.initials: Z
authors.lastname: Bahloul
authors.forename: Francois
authors.initials: F
authors.lastname: Cornelis
authors.forename: Hammadi
authors.initials: H
authors.lastname: Ayadi