一例新发生的5p部分单体合并隐匿18p微小重复

A de novo partial 5p deletion and cryptic 18p duplication detected by SNP-Array in a boy featuring Cri-du-Chatsyndrome ]

目的对1例临床表型严重的疑似猫叫综合征患者的核型进行确诊，为评估该家庭的再发风险提供依据。方法采用高分辨G-显带核型分析患者及其父母，应用猫叫综合征关键区基因位点特异性探针（5p15．2，DSS23／D5S721）、Tel5p／5q、Tel18p／18q亚端着丝粒探针和18号染色体涂染探针进行荧光原位杂交（fluorescenceinsituhybridization，FISH）检测患者及其父母，SNP-Array对患者全基因组DNA进行扫描分析。结果高分辨G显带核型分析发现患者5p末端有微小缺失。应用猫叫综合征关键区基因位点特异性探针荧光原位杂交结果发现患者D5S23／D5S721位点缺失。高密度的SNP-Array芯片检测结果显示该患者5号染色体短臂末端存在15Mb片段的缺失合并18号染色体短臂末端存在约2Mb的重复。应用5P亚端着丝粒探针和18p亚端粒探针进行FISH进一步确定了患者携带一条源于5p和18p易位而来衍生的5号染色体。最终确定其染色体核型为46，XY，der（5）t（5；18）（p15．1；p11．31）dn。结论SNP-Array结合FISH技术确诊了患者为新发生的5p部分缺失合并隐匿的18p部分重复，在其家庭复发风险低。SNP-Array能检出微细的染色体不平衡改变，对于染色体的病因学分析及复发风险评估具有重要价值。

Objective To determine the karyotype of a boy suspected to have Cri-du-Chat syndrome with severe clinical manifestations, and to assess the recurrence risk for his family. Methods High resolution GTG banding was performed to analyze the patient and his parents. Fluorescence in situ hybridization （FISH） with Cri-du-Chat syndrome region probe as well as subregional probes mapped to 5pter, 5qter, 18pter, 18qter and whole chromosome painting probe 18 was performed to analyze the patient and his parents. In addition, single nucleotide polymorphism-based arrays （SNP-Array） analysis with Affymetrix GeneChip Genome-Wide Human SNP Nsp/Sty 6.0 were also performed to analyze the patient. Results Karyotype analysis indicated that the patient has carried a terminal deletion in 5p. FISH with Cri- du-Chat syndrome region probe confirmed that D5S23 and D5S721 loci are deleted. SNP-Array has detected a 15-Mb deletion at 5p and a 2-Mb duplication at 18p. FISH with 5p subtelomeric probes and 18p subtelomeric probe further confirmed that the derivative chromosome 5 has derived from a translocation between 5p and 18p, which has given rise to a 46,XY, der（5）t（5; 18） （p15. 1;pll. 31）dn karyotype. Conclusion A de novo 5p partial deletion in conjunct with a cryptic 18p duplication has been detected in a boy featuring Cri-du-Chat syndrome. His parents, both with negative findings, have a low recurrence risk. For its ability to detect chromosomal imbalance, SNP-Array has a great value for counseling of similar patients and assessment of recurrence risks.