一例发育迟缓合并智力低下患儿的遗传学分析

Genetic analysis of a patient featuring developmental delay and mental retardation

目的确定1例发育迟缓、智力低下的染色体非平衡易位患儿异常核型的来源，探讨单核苷酸多态性微阵列（single nucleotide polymorphisms array, SNP array）技术在染色体异常诊断方面的价值。方法应用常规G显带方法分析患儿及其父母的染色体核型，应用SNParray对患者及其母亲的全基因组DNA进行高分辨率分析。结果患儿核型为45，XY，-15，der（12），t（12；15）（p13．3；q13）mat。患儿父亲染色体核型正常；母亲为平衡易位携带者，核型为46，XX，t（12；15）（p13．3；q13）。患儿继承了母亲的1条衍生的12号染色体，丢失了平衡易位的15号染色体，导致非平衡易位的发生。SNParray分析结果显示患儿12p13．31-p13．33存在6．25Mb的缺失，15q11．2-q13．2存在9．3Mb的缺失，患儿染色体缺失与临床表现密切相关。未发现患儿母亲携带染色体微缺失或微重复。结论母源性12号和15号染色体非平衡易位是导致患儿临床表现的主要原因。通过检测父母的染色体核型可明确异常的类型，和确定患儿异常染色体的来源，高分辨率的SNParray技术能提供更详细、更准确的染色体信息，有助于评估染色体异常的再发风险。

Objective To explore the genetic cause for a child featuring developmental delay and mental retardation. Methods The child was analyzed with G-banded karyotyping and an Ill＇umina Human CytoSNP-12 Beadchip. Results The father of the patient had a normal karyotype. The mother had a karyotype of 46,XX,t（12;15）（p13.3;q13）. The child had a karyotype of 45,XY,der（12）t（12;15）（p13.3; q13）mat,-15. SNP array analysis showed that the child has deletions in 12p13.31-p13.33 and 15q11.2- q13.2. But no deletion or duplication was detected in his mother. Conclusion The unbalanced translocation involving chromosomes 12 and 15 probably accounts for the mental retardation in the child. SNP array is useful for the detection of chromosomal rearrangements and genetic counseling.