Hook E B, Liss S M
J Chronic Dis. 1982;35(3):207-9. doi: 10.1016/0021-9681(82)90141-2.
Different cytogenetic conditions which may produce the same phenotype can be defined as phenotypically homologous. Such conditions may differ in their mean severity. It is suggested here that the age of ascertainment by cytogenetic laboratories of individuals with chromosomal abnormalities is a useful relative index of severity. Three nonmosaic cytogenetic conditions (47, + 21, 47, + 18, and 45, X) were compared with their respective mosaic homologues, using data reported by 38 laboratories participating in the New York State Chromosome Registry. For all three comparisons the mean age of ascertainment and the proportion ascertained in individuals older than 1 yr were greater for the mosaic than the nonmosaic homologues, consistent with the utility of this variable as an index of relative severity. A comparison was also undertaken between (nonmosaic) 45, X and (nonmosaic) 46, long-arm isochromosome-X forms of Turner's syndrome. Only 2% of the latter cases were ascertained under age 1 yr, compared to 25% of the former. The difference is consistent with lesser phenotypic severity of the isochromosome form of Turner's syndrome--a finding of which is independently suggested by a trend in collected heterogeneous case reports.
不同的细胞遗传学状况可能产生相同的表型，这种情况可被定义为表型同源。这些状况在平均严重程度上可能有所不同。本文提出，细胞遗传学实验室对染色体异常个体的确诊年龄是一个有用的严重程度相对指标。利用参与纽约州染色体登记处的38个实验室报告的数据，对三种非嵌合细胞遗传学状况（47，+21、47，+18和45，X）与其各自的嵌合同源物进行了比较。在所有这三种比较中，嵌合同源物的确诊平均年龄以及1岁以上个体的确诊比例均高于非嵌合同源物，这与该变量作为相对严重程度指标的效用一致。还对特纳综合征的（非嵌合）45，X和（非嵌合）46，长臂等臂染色体-X形式进行了比较。后者病例中只有2%在1岁以下被确诊，而前者为25%。这种差异与特纳综合征等臂染色体形式的表型严重程度较低相一致——这一发现由收集的异质性病例报告中的趋势独立表明。
