Mol Cytogenet 2018 29;11:62. Epub 2018 Dec 29.
1Institute of Human Genetics, University Medical Center, Heinrich-Düker-Weg 12, 37073 Göttingen, Germany.
Background: Down syndrome, typically caused by trisomy 21, may also be associated by duplications of the Down syndrome critical region (DSCR) on chromosome 21q22. However, patients with small duplications of DSCR without accompanying deletions have rarely been reported.
Case Presentation: Here we report a 5½-year-old boy with clinical features of Down syndrome including distinct craniofacial dysmorphism and sandal gaps as well as developmental delay. Conventional karyotype was normal, whereas interphase FISH analysis revealed three signals for DSCR in approximately 40% of lymphocytes and 80% of buccal mucosa cells. Array-CGH analysis confirmed a 2.56 Mb duplication of chromosome 21q22.13q22.2 encompassing .
Conclusion: This presents one of the smallest duplications within DSCR leading to a Down syndrome phenotype. Since the dosage sensitive gene is the only duplicated candidate DSCR gene in our patient, this finding supports the hypothesis that contributes to dysmorphic and intellectual features of Down syndrome even in a mosaic state.