Brown Shadow in Lichen Nitidus: A Dermoscopic Marker!

A 35-year-old male presented with asymptomatic multiple papular lesions over both forearms. Physical examination revealed multiple white-colored, flat-topped papules [Figure 1]. Based on the characteristic morphology of the lesions, a clinical diagnosis of lichen nitidus was established.

Figure 1

Multiple white-colored flat-topped papules distributed bilaterally over forearms

Dermoscopy (DermLite III; 3Gen; Polarized, 10×) of the lesions revealed multiple, white, well-circumscribed circular areas, 1–2 mm in diameter with a smooth surface [Figure 2a]. An indistinct brown shadow was reflected through each of these white circles [Figure 2b].

Figure 2

(a) Dermoscopy demonstrates multiple, white, well-circumscribed, circular areas with a smooth surface along with an indistinct brown shadow reflected through these white circles (b) Magnified dermoscopic image of (a) demonstrating the brown shadow (black arrow) (DermLite III; 3Gen; Polarized, 10×)

Histopathology revealed a circumscribed subepidermal dense focal lymphohistiocytic infiltrate along with occasional Langhans giant cells, flanked by collarettes of epidermal acanthosis on either side, which gave a “ball-in-clutch” appearance confirming the diagnosis of lichen nitidus. The overlying epidermis showed evidence of acanthosis and focal parakeratosis [Figure 3].

Figure 3

Histopathology shows subepidermal foci of lymphohistiocytic infiltrate, encircled by acanthotic epidermal collarettes with parakeratosis of overlying stratum corneum (H and E stain 10×)

The presence of multiple well-demarcated white circles on dermoscopy are known to correspond to epidermal acanthosis on histopathology.[12] An interesting observation made was the presence of a brownish shadow inside each of these white circles, which is in fact a reflection of the underlying dense foci of lymphocytes and epithelioid cells in the dermal papilla. This deduction concurs with the observation of the “peripilar sign” in cases of early androgenetic alopecia, wherein the superficial perifollicular lymphocytic infiltrate is seen as a brown halo around the hair follicles.[34] Hence, in lichen nitidus, the epidermal acanthosis corresponds to white circles and the central brownish shadow reflected through the white circles corresponds to the inflammatory infiltrate enveloped by the acanthotic rete ridges.

This particular finding on dermoscopy establishes a strong dermoscopic and histopathological correlation in lichen nitidus, which enables us to differentiate it from other conditions mimicking it, such as pityriasis versicolor and lichen sclerosus et atrophicus.

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Conflicts of interest

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