Elsevier

European Journal of Medical Genetics

Volume 48, Issue 3, July–September 2005, Pages 355-359
European Journal of Medical Genetics

Chromosomal imbalance letter
Trisomy of chromosome 16p13.3 due to an unbalanced insertional translocation into chromosome 22p13

https://doi.org/10.1016/j.ejmg.2005.05.009Get rights and content

Abstract

A dysmorphic boy with severe mental retardation was found on array CGH to have an insertional translocation of chromosome 16p13.3 into the short arm of chromosome 22, karyotype 46,XY,.ish der(22),ins(22;16)(p13;p13.3p13.3) de novo. His clinical features overlap with the reported cases of ‘duplication 16p’ syndrome, namely a round face, hypertelorism, a long philtrum, micrognathia, a thin upper lip, a posterior cleft palate and low set, simple ears, clubbed feet, severe developmental delay, psychomotor retardation and seizures. This 4-year boy with trisomy 16p13.3 has the smallest duplication reported of this critical region, which could not be detected without array CGH. The maximal duplicated region is gene rich and contains about 80 genes and/or candidate genes. Assignment of the genes that contribute to the observed phenotype awaits the characterisation of other patients with small duplications in this region.

Section snippets

Array CGH

Giemsa-banded karyotypes at an 800 band-level obtained from PHA stimulated lymphocyte cultures from the patient and both parents were normal. FISH analysis for deletions of chromosome 22q11 and all subtelomeres was normal as well as the screening of selective exons in the ATRX gene. Array CGH was performed [5].

Chromosomal anomaly

A de novo insertional translocation of chromosome 16p13.3 into the short arm of chromosome 22 was present (Fig. 2, Fig. 3). The minimal size of the insertion is 4.5 Mb, the maximal size 7 Mb (flanking clones within the duplication region are RP11-433P17 at 3.4 Mb and RP11-148F10 at 7.9 Mb).

The karyotype is 46,XY, ish der(22),ins(22;16)(p13;p13.3p13.3) de novo.

This karyotype was confirmed by FISH and also to be de novo as both parents had no translocations.

Clinical description

The maternal serum screening for chromosomal anomalies carried out at 15 weeks gestation in the first and spontaneous pregnancy of a non-consanguineous couple indicated an increased risk of 1 in 72 for trisomy 18. Echography at 16 weeks gestation indicated mild polyhydramnios, marked foetal ascites, an enlarged liver, clubbed feet, relatively short femora, a relatively large biparietal diameter and a thick placenta. A normal male karyotype 46,XY was found on amniocentesis.

Delivery occurred at

Discussion

Pure interstitial trisomy 16p13.3 has only twice previously been reported. A patient with an insertional duplication of 16p–16q, and a familial case resulting from paternal transmission of a chromosome with an ins(1;16)(q42;p13.1p13.3) have been reported [2]. Non-detection in the case reported here was possibly because the resolution of traditional karyotyping could not discriminate between a terminal duplication and duplication at 2 Mb from the telomere. Also, the insertion into the satellites

References (5)

There are more references available in the full text version of this article.

Cited by (0)

View full text