Lichen nitidus

  • Rare
  • Primarily affects children (4 months to 15 years, median age 2-3 years old)
    • Females > Males (2:1 ratio)

  • Unknown etiology
  • Blaschkoid distribution points to somatic mosaicism but genes and triggering factors unknown
  • Putative mechanism:
    1. Somatic mutation produces an aberrant clone of epidermal cells that migrates along lines of Blaschko
    2. Exposure to infectious agent/other precipitant gives rise to a novel membrane antigen
    3. CD8+ T-cell mediated attack of cytotoxic T cells on mutated keratinocyte clones

  • Linear dermatosis made of small (2-4 mm), flat-topped, smooth or scaly, skin-colored to tan (hypopigmented) papules ± vesicles 
  • Unilateral streak along lines of Blaschko on an extremity >>> trunk, head, neck
  • Occasionally bilateral distribution or multiple parallel bands
  • Can overlap with linear lichen planus and blaschkitis
  • Asymptomatic > intense pruritus 
  • Onset over days-weeks 🡪 spontaneous resolution after months-years with post-inflammatory hyperpigmentation
  • Digital involvement may result in onycholysis, splitting, fraying, complete nail loss

  • Lichenoid infiltrate also involving adnexal structures
  • Exocytosis, parakeratosis, dyskeratosis, focal/diffuse vacuolar degeneration in overlying epidermis

  • Linear lichen planus
  • Blaschkitis 
  • Linear graft-versus-host disease
  • Lichen nitidus 
  • Linear porokeratosis
  • Lichen sclerosus
  • Linear Darier

  • Spontaneously resolves within 1-2 years
  • Topical corticosteroids with occlusion can accelerate healing
  • Topical calcineurin inhibitors – helpful for nail dystrophy