Linear facial lichen planus pigmentosus

Linear lichen planus pigmentosus of the face with histological findings of lichen planopilaris - an uncommon variant of lichen planus

“…The disorder has a slight female predilection and is more common in middle-aged patients of Indian, Latin American, African, and Asian heritage [6][7][8]. Unlike other LP subtypes, LPPig often spares the scalp, mucosa, and the nails [6][7][8][9]. Lichen planus pigmentosus presents with bilateral, symmetric blue-gray macules and coalescing patches that more commonly affect sun-exposed areas of the head and neck [10,11].…”

“…These are not mutually exclusive and may coexist in the same patient. Linear LPPig is an uncommon unilateral variant that has been reported in a segmental, zosteriform, or Blaschkoid distribution [8,9,13,14]. The Blaschkoid and segmental configurations more frequently affect the trunk.…”

“…The Blaschkoid and segmental configurations more frequently affect the trunk. Linear LPPig of the face is very rare and to the best of our knowledge, only few cases have been described in the literature [9]. The linearity of the lesions suggests in part a predetermined genetic mosaicism [13,14].…”

“…It is postulated that the affected areas are populated by a group of cells with distinct immunologic and antigenic profiles. Following exposure to an as-of-yet unknown trigger, a mosaic T cell response likely accounts for the presentation in this variant [9,13,14].…”

“…Although the exact etiology of LPPig is yet to be determined, possible precipitators include ultraviolet radiation, hepatitis C infection, and exposure to contact allergens such as nickel, amla oil, mustard oil, and para-phenylenediamine in hair dyes and henna [6][7][8][9]. Other reported triggers include photosensitizing fragrances such as bergamot oil, musk ambrette, and sandalwood oil [9]. The immunopathogenesis of LPPig results from cytotoxic T lymphocytes that recognize and subsequently attack the epidermal keratinocytes [6,15].…”