Chronic heliodermatitis: a morphologic evaluation of chronic actinic dermal damage with emphasis on the role of mast cells.

Descriptions of actinically damaged human dermis have focused on the late stages of elastotic degeneration. This has diverted attention from preceding events, which are important for understanding the sequence of pathologic changes that culminate in the deranged fibrous structures of elastotic dermis. We studied specimens from the back of the necks (exposed) and inner arms (unexposed) of 24 individuals, aged 35-84 yr, by light and transmission electron microscopy. Intense sunlight exposure was common to all. A previously undescribed finding was the presence of a perivenular, histiocytic-lymphocytic infiltrate in which numerous mast cells, often in close apposition to fibroblasts, were observed. We have termed this "chronic heliodermatitis." We postulate that mast cell-derived mediators in conjunction with enzymes released by the infiltrating cells lead to breakdown of elastic and collagen fibers.