Dermatomyositis: clinicopathological correlations.

Dermatomyositis (DM) is a chronic autoimmune disease affecting primarily the skeletal muscle and the skin. Although the diagnosis is usually based upon clinical and laboratory findings, histopathology is helpful for confirmation purposes and is mandatory in amiopathic DM where there is only skin involvement. Histologically, the typical cases are characterized by subtle vacuolar interface alterations with epidermal atrophy, mild capillary ectasia and sparse perivascular lymphocytic infiltrate; these findings are similar to those seen in other connective tissue diseases, especially lupus erythematosus. This review deals with the specific histological findings that can be found in the different presentations of the disease and discuss the most common differential diagnoses. As for many other inflammatory skin diseases, the diagnosis of DM is based on a strict interaction between the dermatologist and the dermatopathologist.