In a HapMap-CEU population, a large block (480 kb) of linkage disequilibrium encompassing KIAA1109/Tenr/IL2/IL21 showed genetic associations with type 1 diabetes mellitus (T1DM) [7,8], RA [8], juvenile idiopathic arthritis (JIA) [9], psoriasis and psoriatic arthritis(PA) [10]. This evidence concerns the gene IL21 and psoriasis.