Objective To define the origin and the precise location of the aberrant fragments on the short arm of the chromosome 8 in a mentally retarded boy, and to understand the mechanism, the characteristic clinical features and the recurrent risk associated with this abnormality. Methods Highresolution chromosomal banding was performed to analyze the karyotype of the patient and his parents,array comparative genomic hybridization (array-CGH) was employed to investigate the precise location of the aberrant fragments, and quantitative real-time PCR was used to confirm the results. Results The rearranged chromosome 8 in the patient was inverted and duplicated for region 8pl 1.2-p23.1, and deleted for region 8p23.1-pter. In between, a 5.70 Mb single copy region was present, which was delimited by the two olfactory receptor gene (OR) clusters. Conclusion This is a case of classic inv dup del(8p) syndrome,which is characterized by severe mental retardation, brain malformation and specific facial dysmorphism, and is induced by non-allelic homologous recombination (NAHR) between the OR genes on 8p23. 1. Prenatal diagnosis should be performed to monitor the recurrent risk of inv dup del(8p), as well as the other three harmful consequences resulted from the same NAHR mechanism. To the best of our knowledge, this is the first case of inverted duplicated 8p syndrome identified in Mainland China.%目的 明确1例智力低下患儿8号染色体短臂异常的片段来源和位置,探讨该异常核型的发生机制、临床表型特征和家庭再发风险.方法 高分辨显带分析患者及其父母外周血染色体核型,比较基因组杂交芯片(array comparative genomic hybridization,array CGH)精细定位拷贝数异常改变的染色体片段区域,荧光定量PCR验证芯片分析结果.结果 患儿异常染色体为8p11.2-p23.1倒位重复和8p23.2-pter缺失;在重复和缺失之间间隔有1个长为5.70 Mb的拷贝数正常片段,嗅觉受体(olfactory receptor,OR)基因簇位于该片段的两端.结论 这是1例典型的inv dup del(8p)综合征,临床上以重度智力低下、大脑发育不良和特殊面容为主要特征,由8p23.1上OR基因簇的重复序列发生非等位同源重组所致.再生育时,不仅要预防inv dup del(8p)的再发风险,还要注意由同一重组机制造成的另外3种不良结局的妊娠风险.就目前所知,这是国内第1例明确诊断的inv dup del(8p)综合征.
展开▼
