Psoriatic Arthritis: a Critical Review

Psoriatic arthritis is a chronic inflammatory arthritis that affects about 5-25% of patients with psoriasis. The prevalence varies from 20-420 per 100,000 population across the world except in Japan where it is 1 per 100,000. Psoriatic arthritis affects both genders equally and in more than half it follows long-standing psoriasis. Psoriatic arthritis has been grouped into five subtypes: distal interphalangeal (DIP) predominant, symmetrical polyarthritis, asymmetrical oligoarthritis and monoarthritis, predominant spondylitis, and arthritis mutilans. Oligoarthritis occurs in nearly 60% during early disease but later polyarticular disease predominates mainly due to evolution of oligoarthritis to polyarthritis. In 50-60% polyarthritis is symmetrical. Dactylitis and enthesopathy are other major features seen in nearly one third of patients. The diagnosis of psoriatic arthritis is easy in the presence of typical skin lesions, however it can also be made in absence of skin lesions using Classification of Psoriatic Arthritis criteria. Though 30-40% of patients develop joint deformities at a follow-up of 5-10 years but most retain good functional status. Clinical damage has a strong relationship with number of swollen joints, erythrocyte sedimentation rate, and duration of arthritis. Radiological damage occurs early and erosions are present in nearly 50% at 10 years of disease. Spinal disease also has good outcome with maintained spinal mobility in majority of the patients. Screening of patients with psoriasis using questionnaire can help in early diagnosis. Nail dystrophy, scalp lesions, and intergluteal/perianal psoriasis are associated with higher chance of development of psoriatic arthritis. Early diagnosis will lead to early treatment and better outcome especially with advent of new drugs.