Phenotypic discordance in monozygotic twins with 22q11.2 Deletion

Hiroyuki Yamagishi, Chihiro Ishii, Jun Maeda, Yoshifumi Kojima, Rumiko Matsuoka, Misa Kimura, Atsuyoshi Takao, Kazuo Momma, Nobutake Matsuo

Research output: Contribution to journalArticlepeer-review

81 Citations (Scopus)


We report on male monozygotic twins with 22q11.2 deletion and discordant phenotypes. The twins had twin-to-twin transfusion syndrome. Twin 1, the smaller of the pair, had Tetralogy of Fallot, a characteristic facial appearance, swallowing dysfunction, anal atresia, short stature, and mental retardation, whereas twin 2 had a characteristic facial appearance but no other signs of the 22q11 deletion syndrome. Fluorescence in situ hybridization analysis showed a microdeletion on chromosome 22q11.2 in both twins. Zygosity analysis gave a probability of monozygosity greater than 99.999%. These observations indicate that environmental factors or postzygotic events play a role in the phenotypic variability in the twins.

Original languageEnglish
Pages (from-to)319-321
Number of pages3
JournalAmerican journal of medical genetics
Issue number4
Publication statusPublished - 1998 Jul 24


  • 22q11.2 deletion
  • Monozygotic twins
  • Phenotypic variability

ASJC Scopus subject areas

  • Genetics
  • Genetics(clinical)


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