Abstract
Riehl’s melanosis is a hyperpigmentary disorder that occurs predominantly on the face and neck. To date, the pathogenesis of Riehl’s melanosis with regards to the melanogenic properties and paracrine melanogenic molecules has not well been studied. This study was aimed to provide a novel perspective on the pathogenesis of Riehl’s melanosis by identifying the relevant paracrine melanogenic molecules in Riehl’s melanosis. Skin biopsies were performed on lesional and normal-appearing perilesional skin of 12 patients with Riehl’s melanosis and 12 age- and sex-matched healthy controls. Histopathological and immunohistochemical staining for paracrine melanogenic molecules was analyzed. The major histopathological findings of Riehl’s melanosis were basal hyperpigmentation, melanocyte proliferation, interface change, dermal pigmentary incontinence, vascular proliferation, and dermal inflammation. Dermal expression intensities of stem cell factor (SCF) and c-kit were increased in the lesional skin of Riehl’s melanosis. In addition, increased expression of epidermal and dermal ET-1 was also observed in the lesional skin of Riehl’s melanosis. Increased tissue expressions of SCF, c-kit, and ET-1 in Riehl’s melanosis support the role of these paracrine melanogenic molecules in the pathogenesis of Riehl’s melanosis. The findings from this study might present useful information on the pathogenetic mechanism of Riehl’s melanosis.
Highlights
Riehl’s melanosis, which is characterized by diffuse slate-gray to brownish hyperpigmentation on the face and neck, was first reported by Riehl in 1917 [1,2]
Based on the above findings, we suggest that basal hyperpigmentation, melanocyte proliferation, interface change, dermal pigmentary incontinence, vascular proliferation, and dermal inflammation were the major histopathological findings of Riehl’s melanosis observed in this study
The proliferation of mast cells is concomitantly associated with the activation of melanocytes via the stem cell factor (SCF)/c-kit pathway [22]. These findings indicate that the increased expression of SCF/c-kit in Riehl’s melanosis might play a role in the pathological mechanism involved in the melanogenesis and inflammation of Riehl’s melanosis
Summary
Riehl’s melanosis, which is characterized by diffuse slate-gray to brownish hyperpigmentation on the face and neck, was first reported by Riehl in 1917 [1,2]. The associated allergen is not usually demonstrated in most of the patients, and the exact pathogenesis of Riehl’s melanosis is yet to be found. Most of the patients with Riehl’s melanosis were reported to improve only slightly in real-world practice despite long-term treatment with various suggested treatment options, including use of low-fluence 1064 nm Q-switched neodymium-doped yttrium aluminum garnet lasering, intense pulsed light, oral tranexamic acid, and topical combination agents [5,6]. Further research is needed to determine the pathogenesis of Riehl’s melanosis to promote good therapeutic responses of the patients. 2liotft1le atettlaenntgiioencthaatiscbveeesnseplasid[7t]o. tHheowceelvluelra,rlaitntldemaottleenctuiolanr phaatshobmeeenchpaaniidsmtos itnhtehecehlyluplearrpaignmd emntoalteiocunloarf Rpaiethhlo’smmecehlaannoissmis.s in the hyperpigmentation of Riehl’s melanosis
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