Arthritic psoriasis, also known as psoriatic arthritis, refers to a group of rheumatoid factor-negative joint crepitations. Most patients develop psoriatic skin lesions first and then gradually develop joint damage. The initial involvement of arthritic psoriasis is in the synovial membrane or attachment points of the joints, resulting in synovitis or attachment point inflammation, swelling and pressure pain in the affected areas. In Europe and the United States, arthritic psoriasis accounts for 10-30% of psoriasis, with a few reports reaching more than 50%; in Japan and Korea, it is also reported to be 5-10%. In China, the composition ratio of arthritic psoriasis in psoriasis is seriously underestimated, less than 1%. Recently, Shandong Institute of Dermatology used high-frequency ultrasound, nuclear magnetic resonance, CT and DR to screen 1,500 psoriasis patients who came to its outpatient clinic for arthritic psoriasis, and found 90 patients with arthritic psoriasis, with a positive rate of 6%, and more than 90% of the patients were diagnosed for the first time. The traditional diagnostic staging of arthritic psoriasis was based on the Moll & Wright criteria, i.e., inflammatory joint crepitations occurring sequentially or simultaneously with psoriatic lesions and negative for rheumatoid factor. There are five clinical types, namely distal interphalangeal arthritis, asymmetric oligoarthritis, symmetric arthritis, disabling arthritis, and ankylosing arthritis. We evaluated the above diagnostic criteria and found that their sensitivity and specificity were only 60% and 80%; while evaluation of the typing criteria suggested that distal interphalangeal arthritis, asymmetric oligoarthritis, symmetric arthritis, and disabling arthritis may be different stages of arthritic psoriasis rather than distinct clinical types. Our study also identified six previously unreported clinical phenotypes in China, including simple attachment pointitis, cremasteropathy, POPP syndrome, mucocutaneous capsulitis, anterior chest wall syndrome (sternoclavicular joint involvement, sternoclavicular stalk joint involvement, and SAPHO syndrome), and palmoplantar pustular arthritis. There are many diagnostic criteria for arthritic psoriasis, and currently CASPAR criteria are mostly used internationally: inflammatory arthritis (necessary condition, and those with a score of 3 or more in the following 5 categories)
(2 points for current lesions, 1 point for history of psoriasis or family history), 2, nail changes (1 point), 3, negative RF (1 point), 4, finger (toe) inflammation (1 point), 5, radiographic evidence (1 point). The Moll&Wright criteria described in traditional textbooks are no longer widely used due to poor sensitivity and specificity. The treatment of arthritic psoriasis is based on non-carrier anti-inflammatory drugs, tretinoin and methotrexate as the first choice. Biological agents can be added when the disease cannot be controlled, and biological agents alone can also receive better results. Early diagnosis and early treatment can effectively prevent the occurrence of arthritic psoriasis deformities. Arthritic psoriasis is one of the few disabling diseases in dermatology, and patients often consult dermatologists in the early stage of the disease before the occurrence of deformities. Studies at home and abroad have shown that arthritic psoriasis is not uncommon, and raising the alertness to arthritic psoriasis and making full use of imaging means in the treatment of psoriasis are the keys to early diagnosis of arthritic psoriasis.