Translocation 4p;21q identified by FISH in a case previously described as “presumptive monosomy 21”

Recently, Lopez-Pajares et al. (1993) reported identification of a translocation between the short arm of a chromosome 5 and the long arm of a chromosome 21 in a patient who was thought to be monosomy 21. This study is the first application of a chromosome 21 painting probe, pBS-21, and fluorescent in situ chromosome hybridization (FISH) to revise an earlier diagnosis of monosomy 21. We have now restudied skin fibroblast cultures, GM00137B, that are still available from another patient previously described as {open_quotes}presumptive monosomy 21{close_quotes} and have found that this case also has a translocation involving chromosomes 21 and 4. The authors urge that all previous cases of what appeared to be monosomy 21 should be re-examined with FISH to confirm or revise the original diagnosis so that genetic counseling of the family may be updated. 3 refs., 3 figs.