PARTIAL TRISOMY MONOSOMY 6Q IN FETAL CELLS AND CVS LONG-TERM CULTURE NOT PRESENT IN CVS SHORT-TERM CULTURE/

A cytogenetic discrepancy in chorionic villi with implications for pre natal diagnosis is described. Chromosome analysis revealed a normal ka ryotype in banded metaphases from short-term culture and a chromosome count of 46 in cells of the long-term culture. After the birth of a ma lformed infant, a structurally aberrant chromosome 6 was found in lymp hocytes and skin fibroblasts. Re-analysis of chorionic villi confirmed the result from short-term culture but disclosed the presence of the structural aberration in cells of the long-term culture. This type of inconsistency is reported for the first time and stresses the importan ce of a numerical and structural analysis of both short-term and long- term culture. The application of three techniques, chromosome banding, comparative genomic hybridization (CGH), and fluorescence in situ hyb ridization (FISH) analysis, was essential to prove that the derivative chromosome carried a combined partial trisomy/monosomy for 6q. The fi ndings are discussed with respect to the origin of the structural aber ration and to the consequences for prenatal diagnosis on chorionic vil li and genetic counselling.