染色体高分辨结合荧光原位杂交鉴定18q末端缺失综合征

18q terminal deletion identified by high resolution chromosome and fluorescence in situ hybridization

目的探讨1例生长发育迟缓,智力低下女性患儿遗传学发病机制及其与复杂临床表现的关系。方法采用高分辨染色体G显带技术确定患儿及其父母核型,应用荧光原位杂交（fluorescencein situhy bridization,FISH）进一步对患儿核型鉴定并对染色体结构畸变精确定位。结果患儿1条18号染色体q21.3至qter缺失,经FISH鉴定可确定为末端缺失,无小片段易位和倒位,断裂点在q21.32~q22.2约2 Mbp大小的区域。18q22.3~q23关键区域发生缺失,涉及包括鞘磷脂碱性蛋白（myelin basic protein,MBP）、促生长激素神经肽受体（galanin receptor type I,GALR1）等基因单倍缺失。核型描述为：46,XX,del（18）（q21.3）.ish del（18）（q21.32q22.2q23）（RP11-4G81＋,RP11-57F7-,qter-）。结论高分辨染色体技术结合FISH有利于判断染色体微小变异并进行较为精确的定位。虽然实验已证实染色体部分缺失与某些基因相关,但MBP与GALR1等基因单倍剂量是否是导致患儿生长发育迟缓的原因还需要进一步的实验证实。

Objective To explore the relationship between complicated clinical situation and genetic etiopathogenisis of a girl with growth retardation and mental retardation. Methods High resolution G-banding was used to examine karyotypes of the girl and her parents.Fluorescence in situ hybridization（FISH） was used to characterize structural aberration and determine breakpoint. Results 18q terminal deletion was identified with breakpoint located on a 2-Mbp region between q21.32 and q22.2 without translocation and inversion.Gene deletions were made in the critical region from 18q22.3 to q23 including myelin basic protein（MBP） and galanin receptor type Ⅰ（GALR1）.Patient＇s karyotype was interpreted as 46,XX,del（18）（q21.3）.ish del（18）（q21.32q22.2q23）（RP11-4G81＋,RP11-57F7-,qter-）. Conclusions High resolution G-banding combined FISH is appropriate for the diagnosis of complicated chromosome aberration.Further research should be done to prove whether haploinsufficiency of MBP and GALR1 is the reason for growth and mental retardation or not.