The main genetic determinant for psoriasis, known as psoriasis susceptibility 1 (PSORS1), is located within the major histocompatibility complex (MHC) on chromosome 6p21.3 (Trembath et al. 1997; Nair et al. 2000), and spanning, according to different authors, from 180 to 250 kb (Nair et al. 2006; Clop et al. 2013). Here, HLA-C is linked to psoriasis.