title: Two histopathological patterns of postinflammatory hyperpigmentation: epidermal and dermal.
abstract: BACKGROUND
  Postinflammatory hyperpigmentation (PIH) commonly occurs, but the histopathological features are not well characterized.
  
  
  METHODS
  A total of 21 PIH patients' medical charts were reviewed. Punch biopsies from lesional and perilesional normal skin were performed. Sections were stained with hematoxylin-eosin, Fontana-Masson, NKI/beteb, microphthalmia-associated transcription factor (MITF), CD68, c-kit, factor XIIIa, MMP-2 and MMP-9.
  
  
  RESULTS
  Fontana-Masson-stained sections suggested two obvious PIH groups: epidermal (13 cases) and dermal (8 cases) pigmentation. The epidermal pigment group had increased epidermal basal pigmentation. The dermal pigment group had marked pigmentation within the upper dermis and decreased epidermal pigmentation. More intense perivascular lymphocytic infiltration was observed in the dermal pigment group. NKI/beteb levels were increased in lesional skin in both groups. The numbers of MITF+ melanocytes were not different between lesional and perilesional normal skin in either group. The expression of CD68 and c-kit was significantly higher in the dermis of lesional skin than in normal skin in the dermal pigment group. MMP-2 expression was upregulated in lesional skin in both groups.
  
  
  CONCLUSIONS
  PIH patients can be classified into two histopathological groups: epidermal and dermal pigmentation. The dermal pigment group showed decreased levels of epidermal pigmentation. This study provides histopathological information that can improve the treatment of PIH.
authors.affiliation: Department of Dermatology, Ajou University School of Medicine, Suwon, Korea.
authors.forename: Ji-Youn
authors.initials: JY
authors.lastname: Park
authors.affiliation: Department of Dermatology, Ajou University School of Medicine, Suwon, Korea.
authors.forename: Ji-Hye
authors.initials: JH
authors.lastname: Park
authors.affiliation: Department of Dermatology, Ajou University School of Medicine, Suwon, Korea.
authors.forename: Sang Jin
authors.initials: SJ
authors.lastname: Kim
authors.affiliation: Department of Pathology, Ajou University School of Medicine, Suwon, Korea.
authors.forename: Ji Eun
authors.initials: JE
authors.lastname: Kwon
authors.affiliation: Department of Dermatology, Ajou University School of Medicine, Suwon, Korea.
authors.forename: Hee Young
authors.initials: HY
authors.lastname: Kang
authors.affiliation: Department of Dermatology, Ajou University School of Medicine, Suwon, Korea.
authors.forename: Eun-So
authors.initials: ES
authors.lastname: Lee
authors.affiliation: Department of Dermatology, Ajou University School of Medicine, Suwon, Korea.
authors.forename: You Chan
authors.initials: YC
authors.lastname: Kim
mesh_terms: D000293:Adolescent; D000328:Adult; D015415:Biomarkers / Q000032:analysis; D002648:Child; D002675:Child, Preschool; D020405:Dermis / Q000473:pathology*; D004817:Epidermis / Q000473:pathology*; D005260:Female; D006801:Humans; D017495:Hyperpigmentation / Q000209:etiology / Q000473:pathology*; D007150:Immunohistochemistry; D007223:Infant; D007249:Inflammation / Q000150:complications*; D008297:Male; D008544:Melanocytes / Q000473:pathology; D008875:Middle Aged; D055815:Young Adult
chemical_list: D015415:Biomarkers
keywords: classification; hyperpigmentation; pathology; skin