title: Hypomelanosis of Ito: pigmentary mosaicism with immature melanosome in keratinocytes.
abstract: BACKGROUND
  Hypomelanosis of Ito is a rare genetic disorder characterized by whorled areas of hypomelanosis. The purpose of the present study was to revisit some aspects of Ito's hypomelanosis.
  
  
  METHODS
  Clinical observations included ultraviolet-light-enhanced visualization (ULEV) method. Histochemistry, immunohistochemistry, and electron microscopy were performed on biopsy samples from the hypopigmented areas and the surrounding skin.
  
  
  RESULTS
  Both the ULEV and microscopic examinations revealed the heterogeneity of the pigmentation. Hypomelanosis was characterized by a reduction in melanosomes, both in melanocytes and keratinocytes. These organelles were immature and atypical, showing a weak tyrosinase immunoreactivity. Melanosome macroautophagy was prominent in keratinocytes. Some clusters of the same cells exhibited strong immunoreactivity for the Mac 387 antibody (Ca(2+) -dependent calprotectin). Ulex europaeus agglutinin-1 (UEA-1) decorated the superficial layers of the epidermis. Such features are typically found in functionally altered keratinocytes. A number of dermal cells exhibited intense phagocytic activity linked to lysozyme immunoreactivity.
  
  
  CONCLUSIONS
  Both the melanosome depletion and macroautophagy of immature melanosomes in keratinocytes appeared to represent prominent aspects of hypomelanosis of Ito. In sum, Ito's hypomelanosis combines structural and functional changes affecting both the melanocytes and keratinocytes in the skin.
authors.affiliation: Department of Dermatopathology, University Hospital of Liège, Liège, Belgium.
authors.forename: Céline
authors.initials: C
authors.lastname: Devillers
authors.forename: Pascale
authors.initials: P
authors.lastname: Quatresooz
authors.forename: Trinh
authors.initials: T
authors.lastname: Hermanns-Lê
authors.forename: Gregory
authors.initials: G
authors.lastname: Szepetiuk
authors.forename: Roland
authors.initials: R
authors.lastname: Lemaire
authors.forename: Claudine
authors.initials: C
authors.lastname: Piérard-Franchimont
authors.forename: Gérald E
authors.initials: GE
authors.lastname: Piérard
mesh_terms: D001343:Autophagy; D006801:Humans; D017496:Hypopigmentation / Q000235:genetics / Q000473:pathology*; D007223:Infant; D015603:Keratinocytes / Q000473:pathology* / Q000648:ultrastructure; D039841:Leukocyte L1 Antigen Complex / Q000032:analysis; D008297:Male; D020460:Melanosomes / Q000235:genetics / Q000473:pathology* / Q000648:ultrastructure; D014442:Monophenol Monooxygenase / Q000378:metabolism; D009030:Mosaicism; D037121:Plant Lectins / Q000032:analysis; D014466:Ultraviolet Rays
chemical_list: D039841:Leukocyte L1 Antigen Complex; D037121:Plant Lectins; C036850:Ulex europaeus lectins; D014442:Monophenol Monooxygenase