Schwartz S, Schwartz M F, Panny S R, Peterson C J, Waters E, Cohen M M
Am J Hum Genet. 1986 May;38(5):741-50.
A male infant was referred for cytogenetic evaluation because of dysmorphic features and developmental delay. In both lymphocytes and skin fibroblasts, a modal number of 46 chromosomes was obtained with an obvious elongation of the long arm of the X chromosome (Xq+). Studies of seven members in 3 generations of this family showed that the proband's mother, sister, and maternal grandmother were phenotypically normal carriers of this abnormal X chromosome. High resolution GTG- and RBG-banding defined the extra chromatin material as an inverted duplication of Xq21----Xq24. This was supported by an approximate twofold increase in alpha-galactosidase A activity, localized to Xq21----q24, observed in the proband's lymphocytes and fibroblasts. BrdU-incorporation studies of the mother's lymphocytes showed the abnormal X to be late replicating in all 100 cells studied and normal alpha-galactosidase A levels. Cytogenetic analysis of the maternal grandmother revealed cytogenetic mosaicism with one cell line containing the abnormal X (37%), and the other, a normal female karyotype (63%). This family is instructive since: (1) it represents only the second case of a dysmorphic male demonstrating a confirmed interstitial partial Xq duplication, and (2) the origin of this familial structural rearrangement has been traced to a grandparental mitotic error.
一名男婴因畸形特征和发育迟缓接受细胞遗传学评估。在淋巴细胞和皮肤成纤维细胞中，均获得了46条染色体的众数，其中X染色体长臂明显延长（Xq+）。对该家族三代中的7名成员进行研究发现，先证者的母亲、姐姐和外祖母均为这条异常X染色体的表型正常携带者。高分辨率GTG和RBG显带将额外的染色质物质确定为Xq21至Xq24的倒位重复。这一结论得到了支持，在先证者的淋巴细胞和成纤维细胞中，位于Xq21至q24的α-半乳糖苷酶A活性大约增加了两倍。对母亲淋巴细胞进行的BrdU掺入研究显示，在所研究的100个细胞中，异常X染色体复制较晚，且α-半乳糖苷酶A水平正常。对外祖母的细胞遗传学分析显示存在细胞遗传学嵌合体，其中一个细胞系含有异常X染色体（37%），另一个细胞系为正常女性核型（63%）。这个家族具有指导意义，原因如下：（1）这是仅有的第二例畸形男性病例，证实存在间质性部分Xq重复；（2）这种家族性结构重排的起源已追溯到祖父母的有丝分裂错误。
