He Yi, Liao Juan-Juan, Liu Ying-Lin, Wen Juan, Lou Ji-Wu
Clin Lab. 2020 Jan 1;66(1). doi: 10.7754/Clin.Lab.2019.190640.
Tetrasomy 18p is a rare disorder. It is known to affect about 250 families worldwide. Tetrasomy 18p is also the most common type of isochromosome. Here we report a de novo tetrasomy 18p.
The copy number variation of the patient was detected by microarray. Whether the abnormal gene was inherited from the parents was detected by karyotype analysis. Then the source of the chromosome was located by fluorescence in situ hybridization. Finally, we used MLPA technology to validate the results of patient testing.
Microarray detection found that patients with 18p11.32p11.21 had duplication, with a copy number of four, which was tetrasomy 18 syndrome. The karyotype results showed 48,XY,+2mar?. Chromosome 18 telomere probe FISH experimental results: 48,XY,+i(18)(p10),+mar.ish. MLPA results showed that the number of chromosome 18 short arm copies is increased. Karyotype analysis results of his mother were 47,XX,+mar. Microarray results showed normal. Karyotype results of his father were normal.
This case is de novo case, the patient's marker chromosome may be inherited from his mother, which does not rule out the influence of his mother's marker chromosome on his isochromosome 18.
18号染色体短臂四体综合征是一种罕见疾病。已知全球约有250个家庭受其影响。18号染色体短臂四体综合征也是等臂染色体最常见的类型。在此我们报告一例新发的18号染色体短臂四体综合征病例。
通过微阵列检测患者的拷贝数变异。通过核型分析检测异常基因是否从父母遗传而来。然后通过荧光原位杂交定位染色体的来源。最后，我们使用多重连接依赖探针扩增（MLPA）技术验证患者检测结果。
微阵列检测发现患者18p11.32p11.21区域存在重复，拷贝数为4，即18号染色体短臂四体综合征。核型结果显示为48,XY,+2mar?。18号染色体端粒探针荧光原位杂交实验结果：48,XY,+i(18)(p10),+mar.ish。MLPA结果显示18号染色体短臂拷贝数增加。其母亲的核型分析结果为47,XX,+mar。微阵列结果显示正常。其父亲的核型结果正常。
该病例为新发病例，患者的标记染色体可能遗传自其母亲，这不能排除其母亲的标记染色体对其18号等臂染色体的影响。
