Schnabel Franziska, Smogavec Mateja, Funke Rudolf, Pauli Silke, Burfeind Peter, Bartels Iris
1Institute of Human Genetics, University Medical Center, Heinrich-Düker-Weg 12, 37073 Göttingen, Germany.
Department of Neuropediatrics, Sozialpädiatrisches Zentrum, Mönchebergstr. 41-43, 34125 Kassel, Germany.
Mol Cytogenet. 2018 Dec 29;11:62. doi: 10.1186/s13039-018-0410-4. eCollection 2018.
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.
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 .
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.
唐氏综合征通常由21三体引起，也可能与21号染色体q22区域的唐氏综合征关键区域（DSCR）重复有关。然而，很少有报道DSCR小重复且无伴随缺失的患者。
我们报告一名5岁半男孩，具有唐氏综合征的临床特征，包括明显的颅面畸形和草鞋足间隙以及发育迟缓。常规核型正常，而间期荧光原位杂交分析显示，约40%的淋巴细胞和80%的颊黏膜细胞中DSCR有三个信号。阵列比较基因组杂交分析证实21号染色体q22.13q22.2存在2.56 Mb的重复。
这是导致唐氏综合征表型的DSCR内最小的重复之一。由于剂量敏感基因是我们患者中唯一重复的候选DSCR基因，这一发现支持了即使在嵌合状态下该基因也导致唐氏综合征畸形和智力特征的假说。
