IL13 and psoriasis: Moreover, a large genome-wide association study, including 3523 cutaneous-only psoriasis cases, 1755 psoriatic arthritis cases, and 5942 unaffected controls, reported that both cutaneous-only psoriasis and psoriatic arthritis were associated with an exonic IL-13 locus on chromosome 5q31 (rs20541) [33]; however, recent analyses suggest that this association is stronger with respect to psoriatic arthritis, or even specific to psoriatic arthritis with no significant association to cutaneous-only psoriasis [34], [35].