The immunocompromised district in dermatology: A unifying pathogenic view of the regional immune dysregulation

Prurigo Nodularis after Radiotherapy: An Isoradiotopic Response?

“…Roucco et al used the term immunocompromised district (ICD) to describe a skin area with local dysregulation of the immune system, which can lead to vulnerability to different skin disorders [3]. An example of such vulnerability can be seen at the site of a previous dermatosis, usually postherpetic.…”

The Puzzle of the Skin Patterns

“…The list of cutaneous insults may be extended to UV or ionising radiation, and new conceptual terms emerge as coined by Ruocco et al [10] such as: (1) isophototopic response: onset of a new skin disease (infections, tumours, dysimmune reactions) in the skin areas exposed to a natural (sun) or artificial (UV lamps) source of UV radiation (lmr); (2) isophototopic non-response or localised cutaneous photoanergy: a skin area exposed to a natural (sun) or artificial (UV lamps) source of UV radiation is selectively spared by a diffuse skin disease (LMR); (3) isoradiotopic response: the onset of a new disease (infection, tumour, or immune dysregulation) on the skin area previously exposed to ionising radiation (lmr); (4) isoradiotopic non-response: a skin area exposed to ionising radiation is selectively spared by a diffuse skin disease LMR); (5) isocaumatopic response: onset of a new skin disorder on a burn scar (lmr); (6) isocaumatopic non-response: a burned skin area is selectively spared by a diffuse skin disorder (LMR); (7) isotraumatopic response: onset of a new skin disorder on a traumatised area (lmr); (8) isotraumatopic non-response: a traumatised skin area is selectively spared by a diffuse skin disorder (LMR).…”

“…A regional immune dysregulation, recently labelled by Ruocco et al [10] as immunocompromised district (ICD), may occur even in immunocompetent individuals. ICD is an umbrella term for skin areas more vulnerable to genetic and acquired insults than the rest of the body.…”

“…Besides these skin patterns, several dermatological phenomena have been described in the literature as responses to various insults showing peculiar skin arrangement: the isotopic response of Wolf, the isomorphic Koebner phenomenon, their inverse variants (the reverse isotopic response or non-response and Renbok phenomenon), and the photo recall phenomenon [10,11,12,13,14,15]. These are not diseases, but define a reaction pattern of a secondary skin disease developing within a variable period of time (days, months, years, decades) after the initial insult.…”

“…ICD is an umbrella term for skin areas more vulnerable to genetic and acquired insults than the rest of the body. The factors responsible for localised immune dysregulation are various and most of the time identifiable by careful clinical history: skin barrier disturbances (structural or functional), cutaneous mosaicism, herpes-infected sites, chronic lymphedema, or heterogeneous skin injuries [10,11,12]. …”