Trisomy 9p with i(9p) and t(9q18p)

Abstract

The trisomy 9p syndrome in a 2-year-old girl with moderate mental retardation is presented. She has a unique karyotype with a de novo isochromosome 9p and a translocation between 9q and 18p.

Centric fission, centromere‐telomere fusion and isochromosome formation: a possible origin of a de novo 12p trisomy

“…The probands phenotype is typical of a "pure" 12p trisomy (Grouchy & Turleau 1982, Ray et al 1985, thus indicating the 8p integrity. This assertion is supported by four previous cytogenetically similar patients who showed the clinical picture correspondent to their short arm trisomies without manifestations of the hypothetical terminal monosomies for lp, 7q, 18p and 2q respectively (Andrk et al 1976, Smith et al 1978, Herva & Koivisto 1979, Leschot & Lim 1979. It should be pointed out that the recent reassessment (Aurias & Dutrillaux 1986) of the 4p trisomy case initially reported by Andrk et al (1 976) revealed an apparent extra duplication of the l p T-band; however, such a concomitant trisomy also lacked a manifest clinical repercussion.…”

“…There are six instances of concurrence of an i(p) and a whole-arm q translocation (onto a nonhomologous telomere) for a single chromosome: three involving the no. 9 (Smith et al 1978, Herva & Koivisto 1979, Sandig et al 1979, two the no. 5 (Leschot & Lim 1979, Orye et al 1983, and one the no.…”

A case of de novo i(12p) with 12q whole‐arm translocation mosaicism

“…Another six instances of concurrence of an i(p) and a whole-arm q translocation onto a nonhomologous telomere (with no evidence of mosaicism) were described that involved chromosomes 4 [Andrk et al, 1976],5 [Leschot and Lim, 1979;Orye et al, 19831 and 9 [Smith et al, 1978;Herva and Koivisto, 1979;Sandig et al, 19791. Characteristics common to these observations include a monocentric appearance of both the isochromosome and the derivative, without demonstrable chromatin loss.…”

Trisomy 7p resulting from isochromosome formation and whole‐arm translocation

“…The second mechanism is supported by the data of Marques-de-Faria and Hackel [1989], in which a patient with trisomy 12p demonstrated 3 clones, all containing an i(12p) but with different translocations of 12q. Nevertheless, when both the formation of an isochromosome and whole-arm transloca- Andre et al, 1976Leschot and Lim, 1979Orye et al, 1983Fujita et al, 1994Present case Smith et al, 1978Herva and Koivisto, 1979Sandig et al, 1979Geneix et al, 1983Delgado et al, 1985Rivera and Rivas, 1992Rivera et al, 1987Marques-de-Faria and Hackel, 1989 tion occur, one of the rearrangements should have adaptive significance for the cell because some "provisional" rearrangements may be very unstable. This observation gives indirect support to the hypothesis concerning the role of secondary rearrangements in complex chromosomal abnormalities [Lurie et al, 19941.…”