In practice, this two-model approach guiding fine mapping was successfully employed to identify alleles segregating at the TRAF1-C5 region conferring susceptibility to rheumatoid arthritis (Schrodi et al., 2007a; Chang et al., 2008) and to fine map the IL23R region in psoriasis (Garcia et al., 2008). This evidence concerns the gene IL23R and psoriasis.