title: Analysis of hyperpigmentation and hypopigmentation after Er:YAG laser skin resurfacing.
abstract: OBJECTIVE
  Pigmentary disorders--such as hyperpigmentation and hypopigmentation, are devastating complications of erbium:yttrium-aluminum-garnet (Er:YAG) laser resurfacing. This study was undertaken to assess the clinical and histopathologic features of hyperpigmentation and hypopigmentation following Er:YAG laser resurfacing, especially in darker skin.
  
  
  METHODS
  One hundred and ninety patients (skin phototypes III and above), treated with Er:YAG lasers--short-pulsed and modulated (variable-pulsed and dual-mode) Er:YAG lasers--for skin resurfacing were recruited. The clinical features of hyperpigmentation and hypopigmentation were evaluated retrospectively using medical charts and serial photographs. For histopathologic examinations, skin biopsies were performed in three patients at hyperpigmentation sites and in four patients at hypopigmentation sites.
  
  
  RESULTS
  Hyperpigmentation was observed in 38.4% of the patients. Mean onset and duration were 3.5 and 7.2 weeks, and then it has faded away within 16 weeks in 93.2% of cases. Hypopigmentation was observed in 13.7% of the patients; its mean onset was 2 months after treatment, and it faded within 1 year in 85% of cases. The incidences and mean durations of these side effects were more intense and longer in patients treated with short-pulsed, variable-pulsed, and dual-mode Er:YAG lasers, in increasing order. In terms of histopathologic examinations, melanin amounts in the epidermal basal layer were observed to vary.
  
  
  CONCLUSIONS
  Hyperpigmentation and hypopigmentation are frequent complications of Er:YAG laser resurfacing. Long pulse duration-induced thermal damage seems to be the most important factor in terms of the induction of pigmentary disorders.
authors.affiliation: Department of Dermatology, Korea University Anam Hospital, #126-1, 5-ga, Anam-dong, Sungbuk-gu, Seoul 136-705, Korea.
authors.forename: Yong Ju
authors.initials: YJ
authors.lastname: Kim
authors.forename: Ho-Sup
authors.initials: HS
authors.lastname: Lee
authors.forename: Sang-Wook
authors.initials: SW
authors.lastname: Son
authors.forename: Soo-Nam
authors.initials: SN
authors.lastname: Kim
authors.forename: Young-Chul
authors.initials: YC
authors.lastname: Kye
mesh_terms: D000328:Adult; D002921:Cicatrix / Q000532:radiotherapy; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D006873:Hydroquinones / Q000627:therapeutic use; D017495:Hyperpigmentation / Q000188:drug therapy / Q000209:etiology* / Q000473:pathology*; D017496:Hypopigmentation / Q000209:etiology* / Q000473:pathology*; D007834:Lasers / Q000009:adverse effects*; D008297:Male; D008875:Middle Aged; D011837:Radiation-Protective Agents / Q000627:therapeutic use; D012075:Remission, Spontaneous; D012189:Retrospective Studies; D013997:Time Factors
chemical_list: D006873:Hydroquinones; D011837:Radiation-Protective Agents; C031927:hydroquinone