Psoriatic arthritis (PsA) is defined as an inflammatory arthritis (IA) associated with psoriasis and is usually negative for rheumatoid factor. This ambiguous definition has impeded research into this subject, but as yet no agreed definition or classification criteria exist for PsA. Furthermore, there are those who question whether PsA exists as a distinct disease, or is a mere coincidence of inflammatory arthritides such as rheumatoid arthritis or ankylosing spondylitis with psoriasis. The pathogenesis of both IA and psoriasis is complex, involving interactions between many different genes and environmental etiological factors. It is likely that PsA is also a complex disease. The identification of genetic susceptibility factors unique to PsA over and above those that contribute to IA or psoriasis alone would put an end to speculation as to whether PsA exists as a distinct disease. In addition, it may aid in the development of novel therapies which target PsA specifically. This review summarizes the approaches taken to identify PsA susceptibility genes, and outlines some interesting regions which may harbor PsA susceptibility genes.
