LOW-LEVEL MOSAICISM FOR BOTH TRISOMY-15 AND MONOSOMY-X IN AMNIOTIC-FLUID CELLS CONFIRMED IN FETAL TISSUES

We report here a case of true fetal mosaicism for both trisomy 15 and monosomy-X; the aberrant cell lines were initially detected at amnioce ntesis as low-level mosaicism (trisomy 15) and multiple-cell pseudo-mo saicism (monosomy-X). In the fetal lymphocytes, only metaphases with a normal chromosome complement were observed. After termination of the pregnancy, various fetal biopsies revealed both trisomy 15 and monosom y-X mosaicism, whereas, at autopsy, no external or internal abnormalit ies could be detected in the fetus. The karyotype can be described as 45,X[15]/47,XY, +15[3]/46,XY[27]. Our results implicate that an additi onal amniocentesis could be more helpful than fetal blood sampling in predicting the fetal karyotype after diagnosis of chromosome mosaicism at amniocentesis. (C) 1998 John Wiley & Sons, Ltd.