title: Discordant blood chimerism in dizygotic monochorionic laser-treated twin-twin transfusion syndrome.
abstract: BACKGROUND
  Twin-twin transfusion syndrome occurs in 10% of monozygotic monochorionic twin gestations and results from an unbalanced exchange of blood from the donor to the recipient fetus through placental anastomoses.
  
  
  METHODS
  We present a case of twin-twin transfusion syndrome with differing fetal sex treated with in utero laser surgery. Genetic analyses showed 46,XX/46,XY hematologic chimerism in both twins at birth and at 6 months, with the recipient twin being significantly more chimeric than the donor. Placental pathologic examination confirmed monochorionicity and laser ablation of all anastomoses.
  
  
  CONCLUSIONS
  Despite in utero separation of the fetal circulations remote from delivery, hematologic chimerism persisted after birth. We speculate that the greater degree of blood chimerism in the recipient compared with the donor was related to the pathophysiology of twin-twin transfusion syndrome before laser surgery.
authors.affiliation: From the Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Keck School of Medicine, University of Southern California, Los Angeles, California; Division of Medical Genetics, Children's Hospital Los Angeles, Keck School of Medicine, University of Southern California, Los Angeles, California; Department of Pathology, School of Medicine, University of California, San Diego, California; Department of Pathology, Children's Hospital Los Angeles, Los Angeles, California; and Valencia Perinatal Center, Valencia, California.
authors.forename: Samer A
authors.initials: SA
authors.lastname: Assaf
authors.forename: Linda M
authors.initials: LM
authors.lastname: Randolph
authors.forename: Kurt
authors.initials: K
authors.lastname: Benirschke
authors.forename: Samuel
authors.initials: S
authors.lastname: Wu
authors.forename: Ramin
authors.initials: R
authors.lastname: Samadi
authors.forename: Ramen H
authors.initials: RH
authors.lastname: Chmait
mesh_terms: D000328:Adult; D001789:Blood Group Antigens; D046528:Chimerism; D005260:Female; D005330:Fetofetal Transfusion / Q000503:physiopathology / Q000601:surgery*; D006801:Humans; D053685:Laser Therapy; D011247:Pregnancy; D014427:Twins
chemical_list: D001789:Blood Group Antigens