Role of Protein Tyrosine Phosphatase (PTPN22) Gene [C1858T] Functional Variant in Genetic Susceptibility of Psoriatic Arthritis in Kuwaiti Arabs

Psoriatic arthritis (PsA) is a chronic, systemic inflammatory arthritic disease characterized by joint inflammation that is associated with cutaneous psoriasis, and can lead to pain, swelling, or stiffness in one or more joints. It results from a complex interplay between genetic, immunologic and environmental factors. A functional variant [C1858T] in the protein tyrosine phosphatase (PTPN22) gene, which encoded Arg620Trp in the lymphoid protein tyrosine phosphatase (LYP) has been shown to be a negative regulator of T-cell activation.

The objective of this study was to investigate an association between PTPN22 gene [C1858T] functional variant and PsA in Kuwaiti patients.

We have investigated the association of PTPN22 gene functional variant in 102 Kuwaiti patients with psoriatic arthritis and compared it to that in 214 healthy controls. The genotypes for the PTPN22 gene [C1858T] variant were determined by using a PCR-RFLP method and confirmed by DNA sequence analysis.

The frequency of homozygous variant genotype (TT) was found to be significantly higher in PsA patients compared to that in the controls (p <0.0001). Collectively, the variant genotype was detected in homozygous and heterozygous combinations in 30% patients (p <0.0001) compared to 16% in the controls. The frequency of variant genotype was found to be highest in the early-onset PsA patients (age >25-34y). No correlation was detected between the variant genotype (TT) and gender in the Kuwaiti PsA patients.

Our data show a significant association of PTPN22 gene functional variant [C1958T] with PsA in Kuwaiti patients and highlight its role in determining the genetic susceptibility along with other factors.