Histopathology of the skin in rheumatic diseases.

Rheumatological systemic autoimmune diseases, such as connective tissue diseases, rheumatoid arthritis or spondyloarthritis, are characterized by the presence of joint involvement associated with extra-articular manifestations. Among them, cutaneous diseases are often the most relevant and representative clinical manifestation, as in psoriatic arthritis, scleroderma or systemic lupus erythematosus. In this context, it is useful for rheumatologists to understand better skin diseases and their histopathological features. Evaluation of skin biopsy specimens can be helpful not only to confirm the diagnosis in both classic and clinically atypical variants, but also to improve further our knowledge of the pathogenetic mechanisms and the close link between skin and articular diseases. In this review, we discuss the clinical features, diagnostic evaluation and the histopathological features of skin manifestation of the most relevant rheumatological autoimmune diseases.