LAUSR

A 60-year-old man who had worked at a cement factory presented with slate-gray–colored hyperpigmentation on his nose and both cheeks (Figure 1A). He had used a cup-shaped dust mask (FFP1 equivalent, Figure 1B) for 4 years at work, and pigmentation along the mask contact area had developed since last year. Histopathologic findings were consistent with RM, showing interface dermatitis patterns with increased dermal melanophages (Figure 1C). Patch tests were performed with the Korean standard series (KOR-1000, Chemotechnique Diagnostics, Vellinge, Sweden) and occluded for 48 hours; the sponge strip and inner and outer surfaces of the mask were also tested “as is.” The sponge provoked positive reactions (+) on day (D)2 and D4 (Figure 1D). The shape and location of the lesion coincided with those of the mask's sponge and the temporal relationship between exposure and symptom, and the patch-test results strongly indicated the diagnosis of mask-induced RM. He moved to a section where mask wearing at work is unnecessary and