Twin and family studies suggest that the genetic contribution to psoriatic arthritis (PsA) is higher than psoriasis, leading to the expectation that there will be genetic loci that contribute to the risk of PsA over and above psoriasis alone. However, few PsA-specific loci have yet been identified. There are several reasons, including lack of power of many studies conducted, to date, and the difficulty of separating pure psoriasis from PsA as many patients with psoriasis may have undiagnosed PsA. Nonetheless, with recent better powered genetic studies, PsA-specific loci are starting to emerge. Examples include the HLA region in which HLA-B27 appears to be primarily associated with PsA whilst HLA-C6 shows a primary association with psoriasis. Outside the HLA gene region, a locus on chromosome 5q31 also shows evidence of association with PsA and not psoriasis. The challenge now remains to identify the genes involved as they could be potential targets for future drug development or to allow screening of patients with psoriasis to identify those at higher risk of developing PsA.
Disclosure of Interest None declared