The variability of clinical manifestation in Riehl’s melanosis: a two-case report

Abstract

Riehl’s melanosis is a rare case of pigmented contact dermatitis on the face that is characterized by hyperpigmented patches secondary to dermal melanin deposits. The clinical manifestations may vary in pattern and color of hyperpigmentation. The most common pattern is reticulate but, in few cases, may present with diffuse pattern. The color may vary from grayish-brown to bluish-brown. We reported two cases of Riehl’s melanosis that consisted of grayish-brown reticulate patches and bluish-brown diffuse patches. Both cases had a history of using cosmetics for a long time before the appearance of the hyperpigmented patches without preceding inflammation. The histopathological examination results of both cases showed vacuolar degeneration of the basal layer, pigmentary incontinence, and infiltration of melanophages and lymphocytes in the dermis that supported the diagnosis of Riehl’s melanosis. The patch test results revealed a positive reaction to 25% balsam peru, 5% nickel sulfate, and suspected cosmetics in the first case and 20% neomycin sulfate and 5% nickel sulfate in the other one. The patients were instructed to avoid the cause and were treated with skin-lightening agent with minor clinical improvement. Riehl’s melanosis has a diagnostic challenge because of the variability of clinical manifestations.