Skin inflammation associated with arthritis, synovitis and enthesitis. Part 1: psoriatic arthritis, SAPHO syndrome, Still's disease, Behçet's disease.

The coincidence of skin and joint inflammation poses a challenge for both dermatologists and rheumatologists. Adequate management of such disorders requires that physicians of both specialties have sound knowledge of the other discipline. In case of suspected joint involvement, familiarity with the diagnostic options available to rheumatologists enables dermatologists to selectively refer their patients for a rheumatology consult. The objective of the present review is to familiarize the reader with the stepwise diagnostic workup performed by rheumatologists today, including laboratory tests, musculoskeletal ultrasound, X-ray studies, and magnetic resonance imaging. Subsequently, we will discuss a number of disorders characterized by the concurrence of skin and joint inflammation, highlighting aspects of epidemiology, etiology and pathogenesis, clinical presentation, diagnosis and treatment. These disorders include psoriatic arthritis as well as autoinflammatory disorders such as SAPHO syndrome, Still's disease and Behçet's disease.