McGinniss M J, Rosenberg C, Stetten G, Schinzel A A, Binkert F, Petersen M B, Kearns W G, Kazazian H H, Pearson P L, Antonarakis S E
Center for Medical Genetics, Johns Hopkins University School of Medicine, Baltimore, Maryland.
Am J Med Genet. 1993 Jul 1;46(6):647-51. doi: 10.1002/ajmg.1320460609.
We report on an 8-year-old girl with minor anomalies consistent with 18q- syndrome and mild developmental delay. Initially cytogenetics showed a terminal deletion of chromosome 21 with mosaicism for a small ring chromosome 21 as the only apparent karyotypic abnormality: mos 45,XX,-21/46,XX,+r(21) (48%/52%). Further studies including FISH and DNA analysis demonstrated a de novo unbalanced translocation of chromosomes 18 and 21 with the likely breakpoints in 18q23 and 21q21.1. Most of 21q was translocated to the distal long arm of one chromosome 18, and this derivative 18 appeared to lack 18q23-qter. The small ring chromosome 21 [r(21)], present in only 52% of the patient's blood lymphocytes, did not appear to be associated with the abnormal phenotype since all 13 chromosome 21 markers that were examined in genomic DNA were present in 2 copies, and the phenotype of the patient was consistent with the 18q- syndrome. The karyotype was reinterpreted as mos 45,XX,-18,-21,+der(18) t(18;21) (q23;q21.1)/46,XX,-18,-21,+der(18) t(18;21) (q23;q21.1), +r(21) (p13q21.1) (48%/52%). These results demonstrate the power of FISH in conjunction with DNA analysis for examination of chromosome rearrangements that may be misclassified by traditional cytogenetic studies alone.
我们报告了一名8岁女孩，她有一些与18q-综合征相符的轻微异常以及轻度发育迟缓。最初的细胞遗传学检查显示21号染色体末端缺失，同时存在一个小的21号环状染色体的嵌合体，这是唯一明显的核型异常：mos 45,XX,-21/46,XX,+r(21) (48%/52%)。包括荧光原位杂交（FISH）和DNA分析在内的进一步研究表明，18号和21号染色体发生了新发的不平衡易位，可能的断点位于18q23和21q21.1。21号染色体的大部分被易位到一条18号染色体的长臂远端，这条衍生的18号染色体似乎缺失了18q23-qter。仅在患者52%的血液淋巴细胞中存在的小的21号环状染色体[r(21)]，似乎与异常表型无关，因为在基因组DNA中检测的所有13个21号染色体标记物均有2个拷贝，且患者的表型与18q-综合征相符。核型被重新解释为mos 45,XX,-18,-21,+der(18) t(18;21) (q23;q21.1)/46,XX,-18,-21,+der(18) t(18;21) (q23;q21.1), +r(21) (p13q21.1) (48%/52%)。这些结果证明了FISH结合DNA分析在检测可能仅通过传统细胞遗传学研究被错误分类的染色体重排方面的作用。
