title: Diprosopus: Systematic review and report of two cases.
abstract: BACKGROUND
  Diprosopus is a subtype of symmetric conjoined twins with one head, facial duplication and a single trunk. Diprosopus is a very rare congenital anomaly.
  
  
  METHODS
  This is a systematic review of published cases and the presentation of two new cases born in Argentina. We estimated the prevalence of conjoined twins and diprosopus using data from the National Network of Congenital Anomalies of Argentina (RENAC).
  
  
  RESULTS
  The prevalence of conjoined twins in RENAC was 19 per 1,000,000 births (95% confidence interval, 12-29). Diprosopus prevalence was 2 per 1,000,000 births (95% confidence interval, 0.2-6.8). In the systematic review, we identified 31 diprosopus cases. The facial structures more frequently duplicated were nose and eyes. Most frequent associated anomalies were: anencephaly, duplication of cerebral hemispheres, craniorachischisis, oral clefts, spinal abnormalities, congenital heart defects, diaphragmatic hernia, thoracic and/or abdominal visceral laterality anomalies. One of the RENAC cases and three cases from the literature had another discordant nonmalformed twin.
  
  
  CONCLUSIONS
  The conjoined twins prevalence was similar to other studies. The prevalence of diprosopus was higher. The etiology is still unknown. The presence of visceral laterality anomalies may indicate the link between diprosopus and the alteration or duplication of the primitive node in the perigastrulation period (12-15 days postfertilization). Pregnancies of more than two embryos may be a risk factor for diprosopus. Given the low prevalence of this defect, it would be useful to perform studies involving several surveillance systems and international consortiums. Birth Defects Research (Part A), 2016. © 2016 Wiley Periodicals, Inc. Birth Defects Research (Part A) 106:993-1007, 2016. © 2016 Wiley Periodicals, Inc.
authors.affiliation: National Network of Congenital Anomalies of Argentina (RENAC), National Center for Genetic Medicine (CNGM), National Administration of Labs and Health Institutes (ANLIS), Buenos Aires, Argentina.|Department of Cellular Biology, Histology, Embryology and Genetics. Medicine College, University of Buenos Aires (UBA), Buenos Aires, Argentina.
authors.forename: María Paz
authors.initials: MP
authors.lastname: Bidondo
authors.affiliation: National Network of Congenital Anomalies of Argentina (RENAC), National Center for Genetic Medicine (CNGM), National Administration of Labs and Health Institutes (ANLIS), Buenos Aires, Argentina.
authors.forename: Boris
authors.initials: B
authors.lastname: Groisman
authors.affiliation: National Network of Congenital Anomalies of Argentina (RENAC), National Center for Genetic Medicine (CNGM), National Administration of Labs and Health Institutes (ANLIS), Buenos Aires, Argentina.
authors.forename: Agostina
authors.initials: A
authors.lastname: Tardivo
authors.affiliation: National Network of Congenital Anomalies of Argentina (RENAC), National Center for Genetic Medicine (CNGM), National Administration of Labs and Health Institutes (ANLIS), Buenos Aires, Argentina.|Neonatology Service in the Evita Pueblo Hospital, Buenos Aires, Argentina.
authors.forename: Fabián
authors.initials: F
authors.lastname: Tomasoni
authors.affiliation: National Network of Congenital Anomalies of Argentina (RENAC), National Center for Genetic Medicine (CNGM), National Administration of Labs and Health Institutes (ANLIS), Buenos Aires, Argentina.|Neonatology Service in the Evita Pueblo Hospital, Buenos Aires, Argentina.
authors.forename: Verónica
authors.initials: V
authors.lastname: Tejeiro
authors.affiliation: National Network of Congenital Anomalies of Argentina (RENAC), National Center for Genetic Medicine (CNGM), National Administration of Labs and Health Institutes (ANLIS), Buenos Aires, Argentina.|Neonatology Service in the 25 de Mayo Hospital, Catamarca, Argentina.
authors.forename: Inés
authors.initials: I
authors.lastname: Camacho
authors.affiliation: National Network of Congenital Anomalies of Argentina (RENAC), National Center for Genetic Medicine (CNGM), National Administration of Labs and Health Institutes (ANLIS), Buenos Aires, Argentina.
authors.forename: Mariana
authors.initials: M
authors.lastname: Vilas
authors.affiliation: National Network of Congenital Anomalies of Argentina (RENAC), National Center for Genetic Medicine (CNGM), National Administration of Labs and Health Institutes (ANLIS), Buenos Aires, Argentina.
authors.forename: Rosa
authors.initials: R
authors.lastname: Liascovich
authors.affiliation: National Network of Congenital Anomalies of Argentina (RENAC), National Center for Genetic Medicine (CNGM), National Administration of Labs and Health Institutes (ANLIS), Buenos Aires, Argentina.
authors.forename: Pablo
authors.initials: P
authors.lastname: Barbero
mesh_terms: D000015:Abnormalities, Multiple / Q000453:epidemiology* / Q000473:pathology / Q000503:physiopathology; D000757:Anencephaly / Q000453:epidemiology / Q000473:pathology / Q000503:physiopathology; D001118:Argentina / Q000453:epidemiology; D054022:Cerebrum / Q000002:abnormalities*; D002972:Cleft Palate / Q000453:epidemiology / Q000473:pathology / Q000503:physiopathology; D005145:Face / Q000002:abnormalities*; D005260:Female; D006330:Heart Defects, Congenital / Q000453:epidemiology / Q000473:pathology / Q000503:physiopathology; D006548:Hernia, Diaphragmatic / Q000453:epidemiology / Q000473:pathology / Q000503:physiopathology; D006801:Humans; D008297:Male; D009436:Neural Tube Defects / Q000453:epidemiology / Q000473:pathology / Q000503:physiopathology; D009666:Nose / Q000002:abnormalities*; D015995:Prevalence; D012307:Risk Factors; D014428:Twins, Conjoined / Q000473:pathology* / Q000503:physiopathology
keywords: conjoined twins; craniofacial duplication; diprosopus; heterotaxy; neural tube defects; very rare congenital anomalies