Psoriatic arthritis.

Psoriatic arthritis (PsA) is a chronic inflammatory arthritis associated with psoriasis. It is found in approximately 10% of psoriatic patients in Japan. PsA mainly affects the peripheral joints, spine, and/or sacroiliac joints. Left untreated, there is progressive, irreversible bone destruction leading to joint deformation and dysfunction. Before the era of biologic treatments, the diagnosis of PsA was difficult and available treatments were limited. Over time the pathology of PsA has become better understood, and many treatments now exist. Early detection and treatment of impending joint deformities are necessary to avoid impairment of PsA patients' quality of life. Most patients develop the arthritis following the onset of the skin manifestations of psoriasis. The process of diagnosing PsA sometimes encounters difficulties because some patients may not show radiographic findings in the early stage, and may have normal levels of C-reactive protein and matrix metalloproteinase-3. For these cases, approaches such as magnetic resonance imaging or ultrasound imaging, as well as symptom questionnaires, are helpful. Currently, non-steroidal anti-inflammatory drugs, disease-modifying antirheumatic drugs, and several biologics are the main treatments for PsA, which when used with an aggressive approach, will result in better patient outcomes.