[Extra-facial Lever granuloma on a herpes zoster scar: Wolf's isotopic response]. / Granulome de Lever extra-facial sur cicatrice de zona : une réaction isotopique de Wolf.

BACKGROUND: Granuloma faciale (GF), or facial granuloma of Lever, is an uncommon dermatosis occurring classically on the face. We report a case of a GF on zoster scars located on the trunk, which is a highly particular isotopic response. PATIENTS AND METHODS: A 60-year-old man with a sole history of left lumbar zoster presented with a skin lesion present for two months. Clinical examination revealed a 2.5-cm papular erythematous lesion that was both infiltrated and pruritic. This lesion was situated precisely on zoster scars. Lab tests revealed no abnormalities. Histopathologic examination showed an inflammatory process without neovessels but rich in eosinophils with chronic vasculitis and polymorphic infiltrate, on which basis GF was diagnosed. DISCUSSION: GF is a localized form of cutaneous small-vessel vasculitis. Although it usually affects the face, extra-facial locations also exist. The original character of this presentation, aside from the location, is the occurrence of this GF on a zoster scar, which corresponds to Wolf's isotopic response. This phenomenon, described by R. Wolf, comprises the occurrence of a new skin disorder at the site of another unrelated and already healed skin disease, usually herpes. The physiopathology is still unclear. This differs from isomorphic reactions such as Koebner's reaction, which consists of the appearance at an injury site of skin lesions typical of an existing dermatosis but not a new disorder. CONCLUSION: This is a rare case of Wolf's isotopic response with GF, of which, to our knowledge, there are no reports in the literature.