Balanced reciprocal translocation mosaicism: New cases and a literature review

Abstract

Mosaicism for a balanced reciprocal translocation is uncommon. These two new cases were detected during investigation of infertility and miscarriages. Otherwise, the probands were normal. Of five previously described cases, only one was possibly syndromal. More reports of this class of chromosomal aberration are needed to assess accurately the risk of phenotypic abnormalities.

Mosaicism with a normal cell line and an unbalanced structural rearrangement

“…It has been postulated that the zygote is initially normal. A postfertilization mitotic exchange between nonhomologous chromosomes and subsequent segregation would result in the normal and balanced rearrangement cell lines [Kleczkowska et al, 1990;Farrell, 1991]. This mechanism could also have produced a mosaic N/UASR as seen in our patient.…”

“…Mosaic normal/balanced reciprocal autosomal rearrangements have also been reported [Fryns and Kleczkowska, 1986;Cantu and Ruiz, 1986;Saura et al, 1987;Kleczkowska et al, 1990;Farrell, 1991;Sciorra et al, 1992;Opheim et al, 1995]. The origin of this type of mosaicism is unknown.…”

Prenatal finding of a fetus with mosaicism for two balancedde novo chromosome rearrangements

“…It has also been suggested by Farrell (1991) that the frequency of chromosomal aberrations in prenatal populations may approximate to the frequencies in the general population because there is a greatly reduced ascertainment on the basis of phenotypic abnormality. In view of the ventriculomegaly in this case, it was reasonable to anticipate other significant findings, however, the mosaicism may have ameliorated the effects of the CCR.…”

Balanced reciprocal translocation mosaicism: How frequent?

“…Reports that have indicated the size of postnatal referral populations in which BRT mosaicism was observed are shown in Table I. With the exception of the report by Farrell [1991], composition of the referral populations appears to be similar. The patients in our population were referred because of a phenotypic abnormality or recurrent spontaneous abortions, or following a spontaneous abortion (products of conception); prenatal and neoplastic cases were not included.…”

“…The patients in our population were referred because of a phenotypic abnormality or recurrent spontaneous abortions, or following a spontaneous abortion (products of conception); prenatal and neoplastic cases were not included. The population in the study by Farrell[1991] was referred entirely on the basis of recurrent abortion. The frequencies of BRT mosaicism in the 2 largest populations reported are 0.19 per 1,000 (this study) and 0.03 per 1,000 [Kleczkowska et al, 19901.…”