Jumping translocations in spontaneous abortions

Chromosome translocations involving one donor chromosome and multiple recip ient chromosomes have been referred to as jumping translocations (JTs). Acq uired JTs are commonly observed in cancer patients, mainly involving chromo some 1. Constitutional forms of JTs mostly involve the acrocentric chromoso mes and their satellites and have been reported in patients with clinical a bnormalities. Recognizable phenotypes resulting from these events have incl uded Down, Prader-Willi, and DiGeorge syndromes. The presence of JTs in spo ntaneous abortions has not been previously described. The breakpoints of al l JTs occur in areas rich in repetitive DNA (telomeric, centromeric, and nu cleolus organizing regions). We report two different unstable chromosome re arrangements in samples derived from spontaneous abortions. The first case involved a chromosome 15 donor. The recipient chromosomes were 1, 9, 15, an d 21, and the respective breakpoints were in either the heterochromatic reg ions or the centromeres. FISH studies confirmed that the breakpoints of the jumping 15 rearrangement did not involve the Prader-Willi region but origi nated at the centromere or in the proximal short arm. A second case of inst ability was observed with a rearrangement resulting from a presumed de novo 8;21 translocation. Three JT cell lines were observed. They consisted of a deleted 8p chromosome, a dicentric 8;21 translocation, and an 80q isochrom osome. The instability regions appeared to be at the pericentromeric region of chromosome 8 and the satellite region of chromosome 21. Both cases prov ed to be de novo events. The unstable nature of the JT resulting in chromos omal imbalance most likely contributed to the fetal loss. It appears that J T events may predispose to chromosomal imbalance via nondisjunction and chr omosomal rearrangement and, therefore, may be an unrecognized cause of feta l loss. Copyrght (C) 2000 S.Karger AG, Basel.