Trisomy 18q‐. Trisomy mapping of chromosome 18 revisited

Abstract

Two patients with trisomy for 18p and the proximal segment of 18q (trisomy 18q –) are reported and compared with similar cases from the literature. The phenotype of trisomy 18q– resembles that of full trisomy 18 but differs mainly in the birdlike face, small mouth, more pronounced microretrognathia, minor skeletal dysplasia and inner organ malformations, and less severe vital prognosis.

De novo duplication of 18p11.21–18q12.1 in a female with anorectal malformation

“…1) A review of the literature revealed that cases of partial trisomy 18, involving euchromatin of both arms are very rare. After exclusion of patients with additional chromosomal abnormalities, combined segmental rearrangements of chromosome 18, isochromosome 18p or 18q, or small supernumerary marker chromosome in the mosaic state [Marical et al, 2007;Rodr ıguez et al, 2007], we were able to identify only three other cases describing duplications of chromosome 18 with overlap to the region observed in our patient (Table II) [Jaffray et al, 1980;Turleau et al, 1980;Wilson et al, 1990]. All three patients had several phenotypic features of full trisomy 18.…”

“…However, two of the three previously described cases with comparable duplications showed microcephaly and developmental delay. The case of Turleau et al [1980] died at 21 days of age because of his congenital diaphragmatic hernia; hence, this case could not be assessed for possible developmental delay.…”

Maternal translocation t(13:18)(q34:q11) and Edwar's syndrome in a fetus: 47, XY, t(13:18)(q34:q11) + 18

“…The critical region in the chromosome 18qll+ 18q12 and 18q22-18qter accounts for the majority of the characteristics of trisomy 18 (Turleau et al 1980). The critical region in the chromosome 18qll+ 18q12 and 18q22-18qter accounts for the majority of the characteristics of trisomy 18 (Turleau et al 1980).…”

Partial trisomy of chromosome 18q11.2-q12: A case report

“…There are several possibilities for why no critical region for Edwards syndrome has been established. Since many of the case reports have been published before high-resolution banding was commonly performed, inaccuracies of the karyotype may have led to misinterpretation of duplicated areas 7,8,10,11) . Alternatively there may be no critical chromosomal region and also the classic phenotype may be due to several noncontiguous chromosomal regions or genes that must be present in three copies to lead to the Edwards syndrome phenotype 16) .…”

“…Although Edwards syndrome is typically associated with duplication of the entire chromosome 18, several individuals with partial trisomy of chromosome 18 have been reported [6][7][8][9][10] . These patients display a range of severity from a relatively mild phenotype with no internal organ malformations to the classic characteristics of Edwards syndrome 11,12) .…”