Arthritis

Abstract

Psoriatic arthritis (PsA) occurs in approximately 20 % of psoriasis patients and is an inflammatory arthritis designated within the “spondyloarthropathy” grouping. Psoriatic arthritis is clinically heterogeneous, with patients typically presenting with stiffness, pain and swelling of the peripheral joints or entire digits, spinal involvement or isolated enthesitis or osteitis-based pathologies. A curious observation in the 1950s was the demonstration that nail psoriasis was more common in PsA than in psoriasis. A more recent observation was that the presence of nail psoriasis is a predictor of the future development of PsA. The nail changes in psoriasis and PsA seem to be fairly similar. Nail disease in psoriasis is associated with a higher burden of subclinical arthritis as determined by ultrasound scanning. Anatomically it is now appreciated that the nail is anchored to the adjacent tendons, ligaments and bones by an elaborate network of entheses (tendon and ligament insertion points). This indicates a close functional and biomechanical integration between the nail and the skeleton and explains the association between nail disease and arthritis.

A number of studies have shown that nail disease in PsA is associated with arthritis of the underlying distal interphalangeal joint, particularly with inflammation at the insertion of the extensor tendon, which is closely associated with the nail matrix.

Diagnosing PsA is important in order to allow for early appropriate treatment. This not only improves symptoms but may also prevent progressive joint damage and destruction. Psoriatic arthritis is a very variable disease, and treatment should be targeted to the manifestations in that patient as well as to the disease severity. The presence of nail involvement in psoriasis thus serves as a guiding beacon to dermatologists that the patient may be at particular risk of arthritis.