Actinically degenerate elastic tissue is the likely antigenic basis of actinic granuloma of the skin and of temporal arteritis.

Staining technique is paramount for detecting and assessing the severe degeneration that occurs in the elastic tissues of the skin and its arteries in response to prolonged exposure to actinic radiation. With a selective "controlled" hematoxylin-and-eosin stain, actinically damaged ("elastotic") elastic tissue stains blue, as Unna described, and contrasts with normal and simply hyperplastic elastic tissue, which stains red. "Special" elastic stains such as Orcein and Verhoeff do not demonstrate this difference. When resorptive (elastolytic) giant cell reactions develop in relation to actinically degenerate elastic tissue of the skin, the papules that arise tend to form expanding, annular rings. A previously used and appropriate name for these autoimmune lesions in the skin is actinic granuloma because this name highlights the likely actinic origin and pathogenesis of many such lesions. Granulomatous inflammation in connection with actinically degenerate internal elastic lamina appears to be the basis of temporal arteritis. Actinic granulomas may occur in the skin concurrently with temporal arteritis. A recent study of temporal arteritis strongly relates its elastic tissue changes to those of "accelerated" atherosclerosis.