一例18q部分缺失综合征患儿的基因型与表型分析

Genotype and phenotype analysis of a child with partial 18q deletion syndrome

目的对1例18q部分缺失的患儿进行基因型与表型的关联分析。方法对1例发育异常患儿行染色体核型分析、单核苷酸多态性微阵列分析（single nucleotide polymorphism array,SNP array）及荧光原位杂交（fluorescence in situ hybridization,FISH）检测。对18q缺失断裂点进行定位，分析基因型与表型的关系。父母行SNParray分析以明确胎儿基因组变异的来源。结果患儿外周血染色体核型为46，XY，del（18）（q23）。外周血基因组DNA的SNParray结果为arr[hg19]18q22．2q23（68158880—78014123）×1，即18q22．2q23末端缺失，大小为9．855Mb。基因组定位分析明确该缺失为18q远端缺失，覆盖多个18q部分缺失综合征的表型关键区域。父母外周血DNA的SNParray结果均未见18q22．2q23微缺失，表明患儿所携带的微缺失为新发变异。患儿外周血中期分裂相FISH结果提示18q末端缺失，验证了SNParray的结果。结论18q22．2q23末端缺失位于18q远端缺失综合征区域，覆盖多个关键致病区域，可能是导致患儿异常表型的主要原因。

Objective To explore the genotype - phenotype correlation of a child with chromosome 18q deletion syndrome. Methods G-banded karyotyping, single nucleotide polymorphism array （SNP array） and fluorescence in situ hybridization （FISH） were performed on the child with abnormal phenotypes. Genotype-phenotype correlation was explored following accurate mapping of the breakpoints on chromosome 18q. SNP array was also performed on the genome DNA derived from peripheral venous blood samples from both parents. Results Chromosomal analysis revealed that the child has a karyotype of 46, XY,del（18）（q23）. SNP array analysis detected a 9. 855 Mb deletion （chr18：68 158 880 - 78 014 123） at 18q22.2q23. Mapping of the breakpoints suggested that the deletion has overlapped with that of distal chromosome 18q deletion syndrome and encompassed several critical regions for this syndrome. SNP array performed on parental samples suggested that the 18q22.2q23 deletion was de novo in origin. FISH analysis of peripheral blood sample from the child confirmed the presence of 18qter deletion. Conclusion The phenotype of this child may be attributed to the deletion of distal 18q22. 2q23, which has encompassed several critical regions for the 18q deletion syndrome.