Stefano Caccavale1, Maddalena La Montagna2, Tobia Caccavale3. 1. Department of Dermatology, Second University of Naples, Naples, Italy. E-mail: stefano85med@libero.it. 2. Department of Psychiatry, University of Foggia, Foggia, Italy. 3. Department of Cardiovascular Surgery and Transplant, Second University of Naples, Naples, Italy.
Sir,We read with great interest the report recently published in the Indian Journal of Dermatology by Kumar et al., which describes a patient with lichen planus pemphigoides presenting over preexisting atrophic scars.[1] The report drew our attention due to the peculiar distribution of the lesions. Kumar et al.[1] note that the case is an extremely rare instance of the isotopic phenomenon. The authors try to clarify the pathomechanism involved in the development of lichen planus pemphigoides at the scarring sites (due to painful ulcers caused by pyoderma gangrenosum). They state that the predilection of the blisters to develop on the lower extremities could be explained by sluggish circulation in those regions. According to their opinion, scars involving the dermis and subcutaneous tissue with largely unaffected epidermis might alter the blood circulation in that particular area, leading to the preferential deposition of immunoglobulins in the scar area and subsequent bulla formation.[1]We think that Kumar's report is no more than a further mere example of “immunocompromised cutaneous district” (ICD).[2] This concept refers to a skin site of loco-regional immune dysregulation due to an obstacle to the normal trafficking of immunocompetent cells through lymphatic channels, and/or interference with the signals that the neuropeptides and neurotransmitters, related to peripheral nerves, send to cell membrane receptors of immunocompetent cells.[2] Disruption of lymph microcirculation and damage to peripheral nerve endings can obviously occur in scarred skin, thus altering the local interplay between immune cells conveyed by lymph vessels and neuromediators running along peripheral nerve fibers.[2] Depending on which of the neurotransmitters and immune cells are involved, this destabilization can be either defective, thus predisposing to infections and tumors, or excessive, thus favoring the occurrence of some immune disorders or dysimmune reactions such as lichen planus pemphigoides. The injuring events capable of rendering a skin region a potential ICD are various.[34567891011121314151617] A recent classification of isomorphic and isotopic skin reactions has proposed a newly coined terminology to indicate each specific cause responsible for the occurrence of an ICD and has encompassed additional conditions that had not been defined previously.[18] The report of Kumar et al. could be seen as an example of “isoscartopic response” (a clinical condition that had not been defined yet). We thank the authors for giving us the opportunity to discuss such a complex and interesting topic.