Psoriatic arthritis: complexities, comorbidities and implications for the clinic.

Psoriatic arthritis (PsA) is a chronic immune-mediated inflammatory disease that affects peripheral joints, entheses and axial sites in addition to both skin and nails. There is considerable evidence to support the assertion that PsA is actually a multisystem disease. Contrary to earlier beliefs, PsA is not only common but also a potentially deforming and disabling disease. In addition to the characteristic extra-articular features, such as uveitis and inflammatory bowel disease, patients with PsA may also suffer from co-existing diseases, referred to as comorbidities. The presence of both extra-articular manifestations and comorbidities may have consequences for the treatment, prognosis and outcome of the disease, which frequently go unrecognized or undertreated. The following review article describes the complexities and comorbidities of PsA as well as their implications for the clinic.