Unveiling the mystery of Riehl's melanosis: An update from pathogenesis, diagnosis to treatment

Abstract

Riehl's melanosis is a hyperpigmentation disorder that has a significant psychological and social impact on individuals. In the past 10 years, new categories have been developed, raising questions about how to classify Riehl's melanosis. The mechanism of this disease remains unclear, although the type IV hypersensitivity response caused by allergic sensitization, as well as genetic, ultraviolet radiation, and autoimmune factors, is to blame. Clinical manifestation, dermoscopy, reflectance confocal microscopy, patch/photopatch testing, histopathology, and a novel multimodality skin imaging system have been used for the diagnosis. A variety of therapies including topical skin‐lightening agents, oral tranexamic acid, glycyrrhizin compound, chemical peels, and lasers and light therapies (intense pulsed light, 1064‐nm Q‐Switched Nd: YAG laser, 755‐nm PicoWay laser, nonablative 1927‐nm fractional thulium fiber laser, new pulsed‐type microneedling radiofrequency), with improved effectiveness. The latest findings on possible biomarkers and their relationship to other autoimmune diseases were also summarized.

Melanin Biopolymers in Pharmacology and Medicine—Skin Pigmentation Disorders, Implications for Drug Action, Adverse Effects and Therapy

“…RM is an acquired hyperpigmentation caused by low-grade allergic contact dermatitis to ingredients in cosmetic products, such as fragrances. Abnormal hyperpigmentation occurs mainly on the face and neck and mainly affects Asian patients [ 110 ]. Post-inflammatory hyperpigmentation (PIH) is an acquired hyperpigmentation that can affect all skin types, but is more common in darker-skinned individuals compared to Caucasians due to more intense melanin pigment biosynthesis [ 111 ].…”

Advancements in Laser Therapies for Dermal Hyperpigmentation in Skin of Color: A Comprehensive Literature Review and Experience of Sequential Laser Treatments in a Cohort of 122 Indian Patients

“…Q-switched (QS) lasers produce short pulses of high-intensity beams and are considered the "gold standard" for treating pigmented lesions [6,13]. Lasers with longer wavelengths, like the 1064 nm QS neodymium: yttrium aluminum garnet (Nd:YAG) laser, can penetrate the dermis more effectively, making them a preferred choice for addressing dermal pigmentation, particularly in dark skin [19]. It targets melanosomes in melanocytes, keratinocytes, and melanophages with its short pulse width and adjustable spot size [3].…”

“…Riehl's melanosis is characterized as an ADMH, manifesting as brownish-grey discoloration on the face and neck. Pigmented contact dermatitis is the term used in cases with a doc-umented history of particular contact allergies [19]. Despite similarities in morphology and histopathology amongst these entities, treatment remains a challenging task with inconclusive outcomes [32].…”

“…(Table 3). However, in practice, the improvement achieved is modest and may not meet the patient's satisfaction, while treatment with topical bleaching agents alone is unsatisfactory [19,34,37]. Combining both, however, may enhance efficacy [33].…”