Miller-Dieker Syndrome due to a 5.5-Mb 17p Deletion in a 17;Y Pseudodicentric Chromosome.

Miller-Dieker syndrome (MDS) is a contiguous gene deletion syndrome in which almost all patients present de novo 17p13.3 deletions. We report on a male infant with MDS and an unusual unbalanced translocation involving chromosomes Y and 17 that resulted in a large 5.5-Mb 17pterp13.2 deletion and a karyotype with 45 chromosomes. Apart from the deletion of the MDS critical region, the deletion of additional distal genes seemed to have no major influence on the patient's phenotype, since he did not show any unusual clinical findings that are not commonly described in MDS patients.

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

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.