一例染色体复杂易位致胎儿多发畸形的遗传学诊断

目的: 对一例染色体复杂易位致多发畸形胎儿进行遗传学分析和诊断。方法: 对一例多发畸形胎儿行G显带染色体核型分析、单核苷酸多态性微阵列（SNP array）及荧光原位杂交（FISH）检测。胎儿父母行外周血染色体核型分析及FISH检测。结果: 胎儿的羊水染色体核型为46，XN，t（12；13）（q22；q32）。SNP array显示胎儿存在1q42.13q44重复（20 192 kb）及15q26.1q26.3缺失（13 293 kb），核型分析与基因芯片结果不一致。FISH验证了SNP array的结果。母亲外周血FISH结果确认为隐匿性46，XX，t（1；15）（q42.1；q26.1）携带者，而胎儿遗传了其中一条衍生的15号染色体der（15）t（1；15）（q42.1；q26.1）。即胎儿遗传了父亲的t（12；13）（q22；q32）平衡易位及母亲的隐匿性平衡易位形成的衍生15号染色体。结论: 1q42.13q44重复和15q26.1q26.3缺失是导致本例胎儿畸形的遗传学病因，产前诊断时多种遗传学技术联合应用可为临床提供准确的诊断。

Genetic analysis of a fetus with multiple malformations caused by complex translocations of four chromosomes

Objective: To conduct genetic analysis in a fetus with complex translocation of four chromosomes. Methods: G-banded chromosome karyotype analysis, single nucleotide polymorphism array (SNP array) and fluorescence in situ hybridization (FISH) were performed in a fetus with multiple malformations. Peripheral blood chromosome karyotype and FISH were also carried out for the parents. Results: The fetal amniotic fluid karyotype was 46, XY, t(12; 13)(q22; q32). SNP array analysis showed that there were 20 192 kb duplication at 1q42.13q44 and 13 293 kb deletion at 15q26.1q26.3 in the fetus. The results of karyotype and SNP array were inconsistent. FISH analyses on the parental peripheral blood samples demonstrated that the mother was a cryptic 46, XX, t(1; 15)(q42.1; q26.1) translocation. The fetus had inherited 46, XY, t(12; 13)(q22; q32) from his father and der(15)t(1; 15)(q42.1; q26.1) from his mother. Conclusions: The 1q42.13q44 duplication and 15q26.1q26.3 deletion may have contributed to the abnormal sonographic features of the fetus. The combination of cytogenetic, SNP array and FISH techniques was beneficial for providing an accurate genetic counseling.