title: Assessment of the thymus at echocardiography in fetuses at risk for 22q11.2 deletion.
abstract: OBJECTIVE
  An absent or hypoplastic thymus is common in patients with 22q11.2 deletion (del22q11.2). We sought to determine whether fetal echocardiography could identify absence of the thymus as a diagnostic tool in pregnancies at risk for fetal del22q11.2.
  
  
  METHODS
  We evaluated the fetal thymus in 16 consecutive pregnancies at risk for fetal del22q11. Fourteen of the fetuses had a conotruncal cardiac lesion, one had a twin with a conotruncal lesion, and in one the mother had a diagnosis of del22q11.2. The fetal thymus assessment was performed by an individual who was not aware of the del22q11.2 status of the fetus.
  
  
  RESULTS
  By 2D imaging, the thymus was identified in the anterosuperior mediastinum as a subtle hypoechogenic area. In nine cases, the thymus was demonstrated prenatally and none had del22q11.2. However, in one case the thymus was only seen on follow-up fetal echocardiography. In six cases, the thymus could not be identified and all six had del22q11.2. In one additional case, analyzed retrospectively, the thymus could not be assessed. The status of the thymus was confirmed on postnatal echocardiography or autopsy in 11 of the 15 cases assessed prenatally.
  
  
  CONCLUSIONS
  Our study suggests that fetal echocardiography can assess the thymus in most cases at risk for del22q11.2. This information may be useful in counseling women/couples who decline amniocentesis or who are awaiting amniocentesis results.
authors.affiliation: The Department of Pediatrics, Division of Cardiology, Fetal Cardiac Program, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Catherine
authors.initials: C
authors.lastname: Barrea
authors.forename: Shi-Joon
authors.initials: SJ
authors.lastname: Yoo
authors.forename: David
authors.initials: D
authors.lastname: Chitayat
authors.forename: Emanuela
authors.initials: E
authors.lastname: Valsangiacomo
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Winsor
authors.forename: Jeffrey F
authors.initials: JF
authors.lastname: Smallhorn
authors.forename: Lisa K
authors.initials: LK
authors.lastname: Hornberger
mesh_terms: D000328:Adult; D002872:Chromosome Deletion; D002892:Chromosomes, Human, Pair 22; D018618:Echocardiography, Doppler, Color / Q000379:methods*; D005260:Female; D006330:Heart Defects, Congenital / Q000150:complications / Q000000981:diagnostic imaging; D006801:Humans; D011247:Pregnancy; D018566:Pregnancy, High-Risk; D016037:Single-Blind Method; D013950:Thymus Gland / Q000002:abnormalities / Q000000981:diagnostic imaging*; D016216:Ultrasonography, Prenatal