title: Monozygotic twins discordant for trisomy 13.
abstract: Monozygotic twins with discordant karyotypes are rare. We report a case of monozygotic twins discordant for trisomy 13 by amniocyte karyotypes. Ultrasound revealed multiple congenital anomalies in Twin A (47,XY,+13), none in Twin B (46,XY), and monochorionic-diamniotic placentation. Zygosity testing performed both prenatally and after birth supported monozygosity. Twin A died in the neontal period. Twin B survived and had normal physical examination, but peripheral blood karyotype revealed 20% mosaicism for trisomy 13. Monochorionic-diamniontic placentation with vascular anastomoses was confirmed by pathological examination. In this paper, we discuss the various mechanisms by which monozygotic twins may have discordant karyotypes. The surviving twin, structurally and developmentally normal at 6 months of age, will be monitored for potential complications of uniparental disomy of chromosome 13 and trisomy 13 mosaicism.
authors.affiliation: Department of Pediatrics, University of Hawaii John A. Burns School of Medicine, Honolulu, HI, USA. karawong@hawaii.edu
authors.forename: K Wong
authors.initials: KW
authors.lastname: Ramsey
authors.forename: T P
authors.initials: TP
authors.lastname: Slavin
authors.forename: G
authors.initials: G
authors.lastname: Graham
authors.forename: G I
authors.initials: GI
authors.lastname: Hirata
authors.forename: V
authors.initials: V
authors.lastname: Balaraman
authors.forename: L H
authors.initials: LH
authors.lastname: Seaver
mesh_terms: D000015:Abnormalities, Multiple / Q000175:diagnosis / Q000235:genetics; D000328:Adult; D046528:Chimerism; D025063:Chromosome Disorders / Q000175:diagnosis / Q000235:genetics*; D002882:Chromosomes, Human, Pair 13 / Q000235:genetics; D004200:Diseases in Twins / Q000235:genetics*; D017809:Fatal Outcome; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007621:Karyotyping; D008297:Male; D009030:Mosaicism; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D014314:Trisomy / Q000175:diagnosis / Q000235:genetics*; D000073839:Trisomy 13 Syndrome; D014430:Twins, Monozygotic; D016216:Ultrasonography, Prenatal; D024182:Uniparental Disomy