RT Book, Section A1 Bianchi, Diana W. A1 Crombleholme, Timothy M. A1 D'Alton, Mary E. A1 Malone, Fergal D. SR Print(0) ID 1106402255 T1 Tetrasomy 12p (Pallister–Killian Syndrome) T2 Fetology: Diagnosis and Management of the Fetal Patient, 2e YR 2015 FD 2015 PB McGraw-Hill Education PP New York, NY SN 978-0-07-144201-5 LK obgyn.mhmedical.com/content.aspx?aid=1106402255 RD 2024/03/28 AB Key PointsCharacterized by tissue-specific presence of an abnormal extra chromosome, which consists of two copies of the short arm of chromosome 12.Abnormal (marker) chromosome is more likely to be found in amniocytes or fibroblasts than blood.Associated with advanced maternal age.Sonographic findings: polyhydramnios, diaphragmatic hernia, rhizomelic short limbs.Main consideration in differential diagnosis is Fryns syndrome.Very poor long-term prognosis. All survivors are mentally retarded.Sporadic inheritance.