1. Genetics
There is a significant genetic factor that increases the susceptibility of psoriatic arthritis in patients with psoriasis. This is highlighted by the fact that 40% of patients with psoriatic arthritis have relatives with the same disease. Studies have found some genes that can be involved in the development of the disease. Most of them are members of the HLA family, including HLA-B7, HLA-DR4, and HLA-B27. Additionally, some gene polymorphisms can be associated with the disease, especially those in the TNF promoter region.