Ring-shaped inflammatory lesions sometimes develop in the abnormal, "elastotic" connective tissues of skin damaged by sun and heat.
The lesions, which commence as papules and nodules, enlarge very slowly and may persist for years. Microscopical sections show that there is an infiltrate composed mainly of foreign-body giant cells, the cells being engaged in digesting and absorbing the abnormal elastotic fibers.
The disorder, which occurs on several continents, should probably be regarded as a phenomenon of repair within dam-aged connective tissue. The name actinic granuloma indicates its external or environmental origin and distinguishes it from other granulomas with which it is constantly being confused.
Actinic granuloma and granuloma annulare appear to be related. In granuloma annulare, a productive and resorptive process also occurs, but its nature remains obscure.
Actinic granuloma may be misdiagnosed as "atypical necrobiosis lipoidica" or as sarcoidosis.
The subject of actinic damage to blood vessels deserves study.
O'Brien JP. Actinic GranulomaAn Annular Connective Tissue Disorder Affecting Sun and Heat-Damaged (Elastotic) Skin. Arch Dermatol. 1975;111(4):460-466. doi:10.1001/archderm.1975.01630160050003