Unusual Duplication in the Pericentromeric Region of Chromosome 9 in a Patient with Phenotypic Alterations

Abstract

Several alterations involving the pericentromeric region of chromosome 9 are considered as normal population variants. These heterochromatic variants or heteromorphisms can include 9qh+, 9cen+, 9ph+, 9ph-, inv(9)(p11q13), and other patterns which can only be defined by FISH studies. However, some heteromorphisms have been found more frequently in patients with several clinical disorders. Here, we report on a patient with intellectual disability, language and neurodevelopmental delay, as well as facial dysmorphism and an unusual chromosome 9. While the banding karyotype was indicative of a simple pericentric inversion of one chromosome 9 [46,XX,inv(9)(p12q13)], array comparative genomic hybridization showed a 6-Mb duplication, including 22 genes: arr[hg19] 9p13.1p11.2(38,869,901- 44,870,714)×3 dn. Molecular cytogenetics using a panel of probes specific for the pericentromeric region of chromosome 9 showed an unusual, rearranged chromosome 9, der(9)(pter→p11.2::q21.11→q12::p11.2→p13.2::q12→p11.2::q21.11→qter), that has not been described before. The patient's phenotypic alterations are probably due to the de novo 6-Mb 9p duplication, although a review of similar cases showed some reports considering this duplication in the euchromatic region as a benign variant. Interestingly, this is the first report of a possible adverse inversion loop formation due to a known heteromorphic pericentric inversion present in the phenotypically normal father of the patient.