Chronic heat-induced skin lesions (Erythema ab igne): Ultrastructural studies

Erythema ab igne (El) is an uncommon skin lesion caused by mild and repeate d exposure to infrared sources. The aim of this study was to investigate th e ultrastructural alterations in this condition. The ultrastructural study was carried out on 5-outpatients who presented typical El of their exposed sites. Skin punch biopsies were processed for standard electron microscopy. The epidermis was hyperpigmented. with focal regressive changes of basal k eratinocytes. An apparent functional activation of melanocytes with numeric al increase of dendritic processes was also observed. The dermis showed abu ndant melanophages and occasional elastic fiber alterations similar to acti nic elastosis. No alterations consistent with preneoplastic skin conditions were observed. The ultrastructural findings associated with El seem to be nonspecific and consistent with moderate regressive changes of keratinocyte s as well as a consensual melanocytic activation and elastic fiber modifica tions. Similar alterations can be observed in chronic actinic skin damage. This condition is presumably more benign than the ultraviolet exposure. The association of El a nd premalignant skin lesions, though occasionally desc ribed, seems relatively infrequent.