Interstitial deletion 5p accompanied by dicentric ring formation of the deleted segment resulting in trisomy 5p13‐cen

Abstract

Karyotypes with an interstitial deletion and a marker chromosome formed from the deleted segment are rare. We identified such a rearrangement in a newborn infant, who presented with macrocephaly, asymmetric square skull, minor facial anomalies, omphalocele, inguinal hernias, hypospadias, and club feet. The karyotype 46,XY,del(5) (pter --> p13::cen --> qter)/47,XY,+dicr(5)(:p13 --> cen::p13 --> cen), del(5)(pter --> p13::cen --> qter) was identified by banding studies and FISH analysis in the peripheral lymphocytes. One breakpoint on the del(5) maps distal to GDNF, and FISH analysis using an alpha-satellite probe suggests that the proximal breakpoint maps within the centromere. The dicentric r(5) consists of two copies of the segment deleted in the del(5), resulting in trisomy of proximal 5p (5p13-cen). The phenotype of the propositus is compared with other trisomy 5p cases and possible mechanisms for the generation of this unique chromosomal rearrangement are discussed.

Mechanisms and Consequences of Small Supernumerary Marker Chromosomes: From Barbara McClintock to Modern Genetic-Counseling Issues

“…At least 11 additional cases of deletion associated with a complementary ring chromosome have been reported in the literature. 31,[48][49][50][51][52][53][54][55][56][57] These cases all involved visible deletions in one homolog, whereas case 7 in this study is the first reported cryptic deletion associated with ring-chromosome formation. Three of the previously reported cases 31,55,57 involve the more rare class of marker chromosomes that do not contain detectable alpha-satellite sequences and are referred to as neocentric markers.…”

Implications of prenatal diagnosis of the fetus with both interstitial deletion and a small marker ring originating from chromosome 5

“…In the literature, there are some mosaic cases of clones with a deletion and an additional ring separately [Gutiérrez‐Angulo et al, 2002; Gereltzul et al, 2008; Kara et al, 2008], but such cases are extremely rare. In newborn infants, only one other case has been reported [Schuffenhauer et al, 1996] with a deletion and a ring of chromosome 5; this baby showed a mosaicism of 46,XY,del(5)/47,XY, del(5),+dic(5), with macrocephaly, asymmetric square skull, minor facial anomalies, omphalocele, inguinal hernias, hypospadias, and club feet. The break points of the deletion shared cen and p13 with those of the dicentric ring chromosome; this case had partial duplication of 5p (p13 → cen), and the mechanisms of del(5) and dic(5) were relatively straightforward.…”

Omphalocele in trisomy 3q: further delineation of phenotype

“…The most common aneuploidies associated with omphalocele are trisomy 18 and 13, Turner syndrome (45, X), and triploidy. Various other chromosomal abnormalities have been found in newborns and fetuses with omphalocele, including rearrangements of 1q (19, 20), 5p (21, 22), partial trisomy 6q (23), and in Miller–Dieker syndrome (MIM #247200) due to 17p deletion (24–26). Here, we present the case of an 11‐month‐old boy with omphalocele who has a duplication of 3q27.3‐qter due to the malsegregation of a maternal t(3;4)(q27.3;q32.3) but does not show the BDLS or dup3q phenotype.…”