Inherited ring chromosomes: an analysis of published cases

Abstract

A review of case reports on patients with ring chromosome revealed 30 individuals (plus two fetuses) who inherited the ring from a total of 23 carrier parents (21 mothers and 2 fathers). The proportion of cases with inherited rings, among all patients with a ring, was calculated to be 5.6% as an upper limit. However, because of a propable difference in survival and fertility between individuals with transmitted and do novo rings, and because of the preferential publication of cases involving inherited rings (and thus a publication bias), the proportion of inherited rings should in reality be no more than 1%. Out of 30 transmitted rings, there were 9 where parent and child were both mosaics, suggesting an inherited instability of the chromosome involved leading to de novo re-formation of the ring in the second generation. The relatively mild clinical manifestations of ring chromosomes, in general, was found to be even more striking in familial cases. In half of the offspring the phenotype was very similar to that of the parent. However, in about a third of cases the offspring were more severely (mentally) affected. This fact should be considered in genetic counseling of clinically normal women who carry a ring chromosome.

Heterochromatin Position Effects on Circularized Sex Chromosomes Cause Filicidal Embryonic Lethality in Drosophila melanogaster

“…In higher eukaryotes, chromosomes are normally linear. However, abnormally circularized ("ring") chromosomes can arise in higher eukaryotes due to chromosome breakage and improper repair (Kistenmacher and Punnett 1970;Kosztolanyi et al 1991;Gisselsson et al 1999). Certain ring sex chromosomes are extremely unstable during mitotic division (Hinton 1955(Hinton , 1959Stone 1982;Gisselsson et al 1999), but the structural basis is poorly understood.…”

Mix Gonadal Dysgenesis Associated with Ring Y Chromosome Mosaics in a Phenotypic Male

“…Copyright © 2009 S. Karger AG, Basel Ring chromosomes are present in 1 in 25,000 human fetuses; 99% arise de novo while less than 1% of rings are inherited [Jacobs, 1981;Kosztolányi et al, 1991;Arnedo et al, 2005]. This chromosomal rearrangement may arise through a cytogenetic mechanism involving breaks in chromosome arms and fusion of the proximal broken ends, leading to a loss of distal material.…”

First familial case of ring chromosome 18 and monosomy 18 mosaicism

“…The proportion of all inherited ring chromosomes is stated to be no more than 1% of all ring chromosomes [Kosztolanyi et al, 1991]. Cases of vertical transmission of ring chromosome 18 from a mother to her offspring, like in our case, have already been described [Christensen et al, 1970;Donlan and Dolan, 1986;Fryns et al, 1992;Jenderny et al, 1993], while mosaicism monosomy 18 with familial ring chromosome 18 is more unusual.…”