MOLECULAR CYTOGENETIC DETERMINATION OF A DELETION DUPLICATION OF 1Q THAT RESULTS IN A TRISOMY-18 SYNDROME-LIKE PHENOTYPE/

We report on an infant who presented at birth with some characteristic s of trisomy 18 syndrome, including low birth weight, facial abnormali ties, overlapping fingers, and congenital heart defects. On chromosome analysis, no additional chromosome 18 was observed and both chromosom e 18 homologues appeared normal. However, a small piece of chromosomal material of unknown origin was detected at the tip of the long arm of chromosome 1. Fluorescence in situ hybridization (FISH) using whole c hromosome 18 painting probes disclosed no additional hybridization at the telomere of 1q, suggesting that the material was derived from anot her chromosome. Further chromosome painting experiments suggested that the telomeric addition was of chromosome 1 origin. To identify subchr omosomal regions involved in the rearrangement, additional FISH analys es were performed using single copy and repetitive DNA probes mapping to different portions of chromosome 1. The analyses showed that probes mapping to 1q34-43 were duplicated in the derivative chromosome 1. In addition, a DNA probe mapping to 1q44 was found to be deleted from th e derivative chromosome 1. Our composite analysis suggests that a dele tion and a duplication of chromosome 1q can result in some of the clin ical findings usually associated with trisomy 18 syndrome. These resul ts demonstrate the usefulness of FISH analysis when karyotype analysis is not consistent with the clinical description. (C) 1994 Wiley-Liss, Inc.