The 620W allele of PTPN22 has been associated with susceptibility to several 
different forms of chronic inflammatory disease, including Type 1 diabetes 
(T1D), rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), and 
autoimmune thyroiditis (AIT). We set out to explore its possible role in two 
other inflammatory diseases: multiple sclerosis (MS) and Crohn's disease (CD). 
In our cohort of 496 MS trios from the United Kingdom, we observed reduced 
transmission of the PTPN22 620W allele. The CD sample consisted of 169 trios as 
well as 249 cases of CD with their 207 matched control subjects collected in the 
province of Québec, Canada; there was also no evidence of association between 
the PTPN22 620W allele and susceptibility for CD. Pooled analyses combining our 
data with published data assessed a total of 1496 cases of MS and 1019 cases of 
CD but demonstrated no evidence of association with either disease. Given the 
modest odds ratios of known risk alleles for inflammatory diseases, these 
analyses do not exclude a role for the PTPN22 allele in susceptibility to CD or 
MS, but they do suggest that such a putative role would probably be more modest 
than that reported so far in T1D, RA, SLE, and AIT.