The American Journal of dermatopathology
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Lichen sclerosus (LS) shares with vitiligo a milky-white appearance. By biopsy, pathognomonic dermal sclerosis readily distinguishes LS from vitiligo and other causes of leukoderma. To determine what the mechanism of hypopigmentation is in LS, we examined samples from LS cases for alterations in melanin content (Fontana-Masson stain) and melanocyte number (HMB-45 [PMEL-17/gp100], Mel-5 [TRP-1], Mart-1 [Melan A]) and compared these findings with those in controls of normal skin, acute scars, vitiligo, and lichen planus (LP; a common inflammatory cause of hyperpigmentation). ⋯ HMB-45-immunoreactive melanocytes were found in the majority of acute scars and in LP and late-stage LS lesions at significantly lower levels than Mel-5- and Mart-1- labeled melanocytes, but they were not found in vitiligo or normal skin. We propose that several mechanisms may play a role in the production of leucoderma in LS: 1) decreased melanin production; 2) block in transfer of melanosomes to keratinocytes; and 3) melanocyte loss. The latter finding may be the pathogenic connection (lichenoid dermatitis of LS triggering an autoimmune reaction to melanocytes) that underlies the documented association of LS with vitiligo.
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Reactive angioendotheliomatosis (RAE) is a rare benign cutaneous vascular proliferation characterized by intravascular hyperplasia of endothelial cells and tuft-like proliferation of vessels. A 75-year-old man had erythematous and violaceous macules, some stellate and others arranged in a livedoid pattern, evolving toward necrosis with central areas having an "atrophie blanche" appearance spread on the trunk, inguinal folds, and right thigh. He was on hemodialysis and had a benign monoclonal gammopathy. ⋯ In this patient, we believe that RAE was caused by obliteration of dermal vessels by amyloid deposits. Indeed, it is thought that RAE could be caused by ischemia secondary to vascular obstruction. This is the first reported patient with RAE associated with amyloid deposits.
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Reactive cutaneous angioendotheliomatosis (RCA) is an uncommon benign disease characterized by intravascular proliferation of endothelial cells. The observation of RCA in infants is exceedingly rare. We describe a case of RCA in a 3-month-old infant. ⋯ Neither an inflammatory infiltrate nor a proliferation of pericytes were present around blood vessels. Intravascular proliferating cells demonstrated positive staining for Ulex europaeus agglutinin 1 (UEA-1) and for Factor VIII-RA and CD34 antigens. The course of the disease was unremarkable with persistence of the lesions for 8 months; no treatment was started.