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.