应用单核苷酸多态性微阵列芯片检测三例21部分三体

SNP array analysis of three cases with partial 21q trisomy

目的对3例21部分三体病例进行检测和分析，明确其重复片段的大小，探讨其基因型与表型的对应关系。方法应用G显带染色体核型分析以及单核苷酸多态性微阵列芯片（single nucleotide polymorphism array，SNP array）对病例进行检测。结果SNParray检测提示3例患者以及其中1例患者的母亲存在21号染色体部分重复，重复的位置和大小不一。例1的21q22．1lq22．3区存在12．35Mb的重复，涉及唐氏综合征关键区，为新发突变；例2的9p24．3p13．3区存在35．32Mb的重复合并21q11．2q21．3区14．42Mb的重复。其中9号染色体的重复包含9p部分三体综合征的关键区，但21号染色体的重复未包含唐氏综合征关键区，且继承自其母亲；例3的21q11．2q21．I区存在4．i7Mb的4倍重复，未包含唐氏综合征关键区，且为嵌合体，其母亲的21q11．2q21．1区存在4．17Mb的3倍重复，亦为嵌合体。结论21部分三体有多种形式，临床表型异质性较大。联合应用多种检测技术尤其是SNP array对于诊断21部分三体、明确基因型和表型的对应关系至关重要。

Objective To analyze three cases with partial 21q trisomy, and correlate their genotypes with phenotypes. Methods G-banding chromosomal analysis and single nucleotide polymorphism （SNP array） were performed for the three cases and their parents. Results SNP array has detected partial 21q trisomy in three cases and one mother, with variable size and location of the duplications. Case 1 harbored a 12.35 Mb duplication at 21@2. 11q22. 3, which spanned the Down syndrome critical region. Case 2 harbored a 35.32 Mb duplication at 9p24. 3p13.3 and a 14.42 Mb duplication at 21q11. 2q21. 3, with the former spanning the partial 9p trisomy syndrome critical region excluding the Down syndrome critical region, and was inherited from his mother. Case 3 harbored a 4.17 Mb tetraploidy at 21q11.2q21.1 in the form of mosaicism, which spared the Down syndrome critical region. His mother carried a 4.17 Mb triploidy at 21q1.2q21.1, which was also a mosaicism. Conclusion Partial 21q trisomy may occur in various forms and its clinical phenotypes are heterogeneous. Combined use of genetic techniques, particularly SNP array, is crucial for diagnosing partial 21q trisomy and delineating its genotype-phenotype correlation.