Richkind K E, Mahoney M J, Evans M I, Willner J, Douglass R
Vivigen Laboratory, Santa Fe, NM 87505.
Prenat Diagn. 1991 Jun;11(6):371-6. doi: 10.1002/pd.1970110605.
Five cases of mosaicism for an isochromosome of 20q have been detected from a total of 50,000 cases analysed for prenatal diagnosis by amniocentesis. Karyotypes were designated mos 46,X-/46,X-,i(20q). In all cases, the abnormal cell line was detected in more than one primary culture, thus fulfilling the criterion for true (level III) mosaicism. Indications for prenatal diagnosis were parental anxiety (two cases), low maternal serum alpha-fetoprotein (AFP) (two cases), and high maternal serum AFP (one case). Level II ultrasounds on all five fetuses were normal, and the abnormal cell line was never detected in fetal blood and/or cord blood. All five pregnancies were continued and had normal outcomes, with birth weights ranging from 2.4 to 3.8 kg. The development of all five children has been normal, with the oldest child in the study now 4 years of age. We suggest that the abnormal cell line in each case was of extrafetal origin, and that this may be one of the more common examples of this phenomenon, occurring in approximately 1/10,000 prenatal diagnoses. Mosaicism i(20q) may have been missed in the past because of the higher resolution necessary to detect this subtle change.
在总共50000例接受羊膜腔穿刺术进行产前诊断分析的病例中，检测到5例20号染色体长臂等臂染色体的嵌合体。核型被指定为mos 46,X-/46,X-,i(20q)。在所有病例中，异常细胞系在不止一次原代培养中被检测到，从而符合真正（III级）嵌合体的标准。产前诊断的指征包括父母焦虑（2例）、孕妇血清甲胎蛋白（AFP）水平低（2例）和孕妇血清AFP水平高（1例）。所有5例胎儿的II级超声检查均正常，且在胎儿血液和/或脐带血中从未检测到异常细胞系。所有5例妊娠均继续进行，结局正常，出生体重在2.4至3.8千克之间。所有5名儿童的发育均正常，该研究中年龄最大的儿童现已4岁。我们认为，每例中的异常细胞系均起源于胎儿外，这可能是这种现象较常见的例子之一，大约每10000例产前诊断中就会出现1例。由于检测这种细微变化需要更高的分辨率，过去可能遗漏了20号染色体长臂等臂染色体嵌合体。
