de Pater J M, Govaerts L C P, de Man S A, van der Sijs-Bos C J M, Christiaens G C M L, van Dam W M, Loneus W H, Engelen J J M
Department of Biomedical Genetics, University Medical Centre, Utrecht, The Netherlands.
Prenat Diagn. 2003 Sep;23(9):747-51. doi: 10.1002/pd.653.
This study aimed to identify a marker chromosome and characterize the short arm of a derivative chromosome 5 in a foetus with the following karyotype: mos 47,XX,del(5)(p?),+i(5)(p10)[50]/48,XX,del(5)(p?),+i(5)(p10),+mar[25].
Amniocentesis was performed in the 26th week of pregnancy because of ultrasound abnormalities (polyhydramnion and decreased amount of gastric filling). All classic banding techniques were performed. FISH and microdissection combined with reverse painting were used to reveal the exact origin of the marker and any extra material on the deleted chromosome 5p. The parents decided to continue the pregnancy and we compared the clinical features of the child born in week 34 with data from the literature on trisomy 5p. The possible contribution of trisomy of the centromeric region of chromosome 8 and trisomy 8p23.3-->8pter to this clinical picture was evaluated.
GTG banding showed one normal and two aberrant chromosomes 5 [del(5)(p?) and i(5)(p10)] in all the cells examined. Furthermore, a supernumerary marker chromosome was present in approximately 30% of the cells. The marker was CBG positive and positive with the pancentromere probe, but dystamicinA/DAPI negative. It did not contain NOR-positive satellites. FISH proved this marker to be derived from the centromeric region of chromosome 8. MicroFISH disclosed the aberrant chromosome 5 as der(5)t(5;8)(p10;p23.3). The parent's karyotypes were normal. The baby showed the characteristic features of trisomy 5p syndrome. She died at the age of 15 days after cardiorespiratory arrest.
The karyotype was interpreted as mos 47,XX,add(5)(p10).rev ish der(5)t(5;8)(p10;p23.3),+i(5)(p10) (WCP5+,D5S23+)[50]/48,XX,add(5)(p10).rev ish der(5)t(5;8)(p10;p23.3),+i(5)(p10)(WCP5+,D5S23+),+mar.ish 8(p10q10)(D8Z2+,WCP8-)[25]. Therefore, the baby had complete trisomy 5p, with trisomy of the distal part of 8p and of the centromeric region of chromosome 8. The clinical significance of de novo marker chromosomes is a major problem in prenatal counselling. Molecular cytogenetic tools such as FISH and microFISH are indispensable for characterizing markers and determining the breakpoints more precisely in deleted chromosomes.
本研究旨在鉴定一条标记染色体，并对一名核型为mos 47,XX,del(5)(p?),+i(5)(p10)[50]/48,XX,del(5)(p?),+i(5)(p10),+mar[25]的胎儿的衍生5号染色体短臂进行特征分析。
因超声异常（羊水过多和胃内充盈量减少），于妊娠第26周进行羊膜腔穿刺。采用了所有经典的显带技术。荧光原位杂交（FISH）和显微切割结合反向绘画技术用于揭示标记染色体的确切来源以及缺失的5号染色体短臂上的任何额外物质。父母决定继续妊娠，我们将第34周出生的孩子的临床特征与文献中关于5号染色体短臂三体的数据进行了比较。评估了8号染色体着丝粒区域三体和8p23.3→8pter三体对该临床表型的可能影响。
GTG显带显示，在所有检测的细胞中，有一条正常的5号染色体和两条异常的5号染色体[del(5)(p?)和i(5)(p10)]。此外，约30%的细胞中存在一条额外的标记染色体。该标记染色体CBG染色阳性，着丝粒探针检测呈阳性，但地霉素A/ DAPI染色阴性。它不包含NOR阳性卫星。FISH证实该标记染色体来源于染色体8的着丝粒区域。显微FISH显示异常的5号染色体为der(5)t(5;8)(p10;p23.3)。父母的核型正常。婴儿表现出5号染色体短臂三体综合征的特征性表现。她在心肺骤停后15天死亡。
核型解释为mos 47,XX,add(5)(p10).rev ish der(5)t(5;8)(p10;p23.3),+i(5)(p10) (WCP5+,D5S23+)[50]/48,XX,add(5)(p10).rev ish der(5)t(5;8)(p10;p23.3),+i(5)(p10)(WCP5+,D5S23+),+mar.ish 8(p10q10)(D8Z2+,WCP8-)[25]。因此，该婴儿为完全性5号染色体短臂三体，伴有8号染色体短臂远端和着丝粒区域三体。新发标记染色体的临床意义是产前咨询中的一个主要问题。诸如FISH和显微FISH等分子细胞遗传学工具对于标记染色体的特征分析以及更精确地确定缺失染色体的断点是必不可少的。
