title: Twin pregnancy with a chimeric androgenetic and biparental placenta in one twin displaying placental mesenchymal dysplasia phenotype.
abstract: OBJECTIVE
  The aim was to report an unusual trizygotic pregnancy that resulted in live-born twins. The placenta of one twin had placental mesenchymal dysplasia (PMD), which resulted from a chimeric fusion of an androgenetic zygote and a normal biparental zygote. The literature review was summarized.
  
  
  METHODS
  The case was first detected by prenatal ultrasound, and was then followed by a histologic and detailed genetic investigation. The literature on PMD, complete hydatidiform moles (CHMs), and placental mosaicism and chimerism was also reviewed.
  
  
  RESULTS
  One placenta of a twin pregnancy was noted to be diffusely cystic and enlarged. The macroscopic and microscopic findings were consistent with the diagnosis of PMD; however, genetic findings confirmed confined placental chimerism involving a normal biparental 46,XY male conceptus and an androgenetic 46,XX complete hydatidiform mole.
  
  
  CONCLUSIONS
  This case represents a rare placental abnormality, PMD, which may have a diverse etiology. Therefore, detailed histologic and genetic analysis were performed for an accurate diagnosis.
authors.affiliation: Department of Pathology, University of Pittsburgh School of Medicine, Magee-Women's Hospital, Pittsburgh, PA 15213, USA. usurti@mail.magee.edu
authors.forename: Urvashi
authors.initials: U
authors.lastname: Surti
authors.forename: Lyndon M
authors.initials: LM
authors.lastname: Hill
authors.forename: Jeanette
authors.initials: J
authors.lastname: Dunn
authors.forename: Tracy
authors.initials: T
authors.lastname: Prosen
authors.forename: Lori
authors.initials: L
authors.lastname: Hoffner
mesh_terms: D046528:Chimerism; D005260:Female; D006391:Hemangioma / Q000473:pathology; D006801:Humans; D006828:Hydatidiform Mole / Q000175:diagnosis*; D008297:Male; D009030:Mosaicism; D010920:Placenta / Q000473:pathology*; D010922:Placenta Diseases / Q000175:diagnosis*; D011247:Pregnancy; D011248:Pregnancy Complications; D011272:Pregnancy, Multiple; D014429:Twins, Dizygotic / Q000235:genetics*