title: Infantile perineal protrusion: a statistical, clinical, and histopathologic study.
abstract: BACKGROUND
  Review of the literature of the peculiar nodule in the perineum of female infants disclosed that the analysis of incidence by gender, observation of the course, histopathologic assessment, and the pathogenesis of the abnormality was suboptimal.
  
  
  OBJECTIVE
  We therefore planned to study a large number of children to analyze the incidence by gender, the course, and the pathogenesis of the peculiar perineal nodules.
  
  
  METHODS
  Of 500 children (224 boys and 276 girls) who ranged from newborn to 11 years of age, occurrence of the perineal nodules was checked. When nodules were found, the site, shape, size, number, and the onset were examined. Histopathologic examination and observation of the course were carried out in some cases.
  
  
  RESULTS
  None of the boys in our population had nodules, but 13% of the girls did. These lesions always occurred as a single peanut-, hen's crest-, or tongue tip-shaped nodule on the perineal midline, and 93% of the lesions had been present since birth. Histologically, the nodule was an outward projection of essentially normal, redundant skin, showing no evidence of lichen sclerosus et atrophicus.
  
  
  CONCLUSIONS
  In view of these findings, we conclude that perineal nodules are a kind of developmental anomaly occurring mostly in girls.
authors.affiliation: Department of Dermatology, Hirosaki University School of Medicine, Hirosaki, Japan. katsuto@cc.hirosaki-u.ac.jp
authors.forename: R
authors.initials: R
authors.lastname: Konta
authors.forename: I
authors.initials: I
authors.lastname: Hashimoto
authors.forename: M
authors.initials: M
authors.lastname: Takahashi
authors.forename: K
authors.initials: K
authors.lastname: Tamai
mesh_terms: D000293:Adolescent; D001004:Anus Diseases / Q000473:pathology*; D002648:Child; D002675:Child, Preschool; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D010502:Perineum; D012737:Sex Factors; D012871:Skin Diseases / Q000473:pathology*