Partial trisomy 7p in two families resulting from different balanced translocations

Abstract

Two families are described in which a balanced translocation producing partial trisomy 7p is segregating. Comparison is made of the phenotype produced by this aneuploidy with other cases in the literature and contrasted with that produced by partial deletion of 7p.

De novo direct tandem duplication of a small segment of the short arm of chromosome 7 (p21.22→22.1)

“…A review of 20 cases was presented by Milunsky et al (1989), and showed that the breakpoints were mainly at p l l , p13, p15, and p21+pter. The breakpoints 7p21 and 7p15 are most frequently involved in translocations resulting in live births (Moore et al 1982).…”

Chromosomal imbalance in the offspring of translocation carriers involving 7p

“…Although from our five family studies it is tempting to suggest that the lethality associated with imbalance for 7p seems to be related to the amount of material involved, this does not agree with the earlier death of two patients with trisomy for the region 7pl5+pter, as in case 1 in the report of Berry et al (1979) and case 1 of this paper, compared to the case with trisomy for almost all of 7p (Carnevale et al 1978). Following the table reported by Moore et al (1982), a comparison is made between our three patients and those reported until now, showing that 7p15 and 7p21 are most frequently involved in translocations resulting in livebirths partially trisomic for 7p.…”

“…Although it has not been suggested that 7p is more susceptible than other regions to breakage and/or abnormal realignment during meiosis, we have found this chromosomal region to be most frequently involved in translocations in our diagnostic karyotype analysis. Partial trisomy 7p has been reported in only a few cases, seven of which were reviewed by Moore et al (1982), but it has not yet been possible to establish a strict relationship between this duplicated chromosomal materia1 and specific and consistent malformations.…”

Congenital cardiovascular malformations (CCVM) and structural chromosome abnormalities: a report of 9 cases and literature review

“…The infant died at 4 months of age. Seven of 12 cases (58%) of similar karyotype abnormalities had at least one CCVM, including two PDA and two VSD (29%, 17%) (Smith et al 1969, Caspersson et al 1971, Larson et al 1977, Carnevale et al 1978, Berry et al 1979, Miller et al 1979, Moore et al 1982, Cantu et al 1985. There were four other CCVMs that were identified only in single patients, including one case with tetralogy of Fallot (TOF) and one with atrioventricular (AV) canal.…”