The PTPN22 1858T variant is not associated with primary biliary cirrhosis

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Abstract
The minor allele of a single nucleotide polymorphism (SNP) in the PTPN22 gene (1858T) encoding the Lyp‐tyrosine phosphatase has been recently associated with multiple autoimmune disorders, raising the possibility that this variant may also represent a risk allele for primary biliary cirrhosis (PBC). We therefore investigated the possible association of the PTPN22(1858T) variant with PBC in a Canadian population. We studied 160 Caucasian patients with biopsy and antimitochondrial antibodies (AMA)‐proven PBC who were genotyped for the PTPN22(C1858T) SNP using a single‐base primer extension assay and mass spectrometry. The frequency of the PTPN22(1858T) allele was then compared between the patients and 290 healthy controls. No association was detected between the PTPN22(1858T) allele and PBC, the frequency of this variant being similar in patients with PBC (7.5%) and controls (8.4%). Restricting the analysis to patients with PBC with any second autoimmune condition or specifically with sicca syndrome or autoimmune thyroid disease also revealed no association with this variant. Thus the PTPN22(1858T) variant is not associated with PBC or with the combination of PBC and a second autoimmune disease. These data suggest that this variant does not confer risk for PBC and does not account for the frequent presence of other autoimmune diseases in patients with PBC.