PRENATAL-DIAGNOSIS OF A FAMILIAL INTERCHROMOSOMAL INSERTION OF Y-CHROMOSOME HETEROCHROMATIN

An apparently unbalanced karyotype containing an abnormal chromosome 1 1 was identified in a 16-week female fetus by analysis of cultured amn iocytes, Fluorescence in situ hybridization (FISH) with a chromosome 1 1 paint identified the presence of an insertion in band 11q24, Parenta l karyotyping documented an unbalanced karyotype with the same der(11) chromosome in the phenotypically normal father, CBG-banding and FISH identified the insertion to be Yq12 heterochromatin: 46,XY, der(11)ins (11;Y) (q24;q12q12).ish der(11) (wcp11+,DYZ1+), The same der(11) chrom esome was also found in the phenotypically normal paternal grandmother , demonstrating this additional Y chromosomal material did not affect normal female sexual development or fertility. The parents elected to continue the pregnancy and a normal girl was born at term, further con firming that this rare familial variant has no clinical significance. This case illustrates the importance of family studies, appropriate ba nding, and FISH analyses to accurately characterize apparent chromosom al abnormalities. (C) 1997 Wiley-Liss, Inc.