Mosaic deletion 11p13 in a child with dopamine beta-hydroxylase deficiency--case report and review of the literature.

Dopamine beta-hydroxylase (DBH) deficiency is characterized by a lack of sympathetic noradrenergic function. Affected individuals exhibit profound deficits in autonomic regulation of cardiovascular function. The diagnosis of DBH deficiency is based on clinical findings, biochemical studies, and sequencing of DBH gene. We report here the characterization of a mosaic cytogenetic abnormality detected by array-CGH in a 16-year-old female with primary DBH deficiency together with dysmorphic features. These features could not be explained by DBH deficiency leading to further investigation. Karyotype was reported normal (46,XX), while a targeted genomic array-CGH revealed a mosaic loss for a segment of at least 1 Mb across 11p13. This segmental loss included the PAX6 and WT1 genes within the WAGR syndrome critical region. Interestingly, the derivative chromosome 11 was observed only in about 28% of cells analyzed. Utilizing a genome-wide oligonucleotide-based array, the deletion segment was estimated to encompass a segment of approximately 10 Mb. Mosaic deletions of 11p13 in WAGR are extremely uncommon. In this case it is distinctly possible that the patient's bilateral iris colobomata might be a manifestation, albeit abbreviated, of the haploinsufficiency for PAX6. This case highlights the importance of cytogenetic analysis when a mutation alone cannot account for the complete phenotype. It also emphasizes the enhanced ability of high-resolution array-CGH techniques in accurately detecting subtle rearrangements in a mosaic form. Finally, it demonstrates the possible phenotypic effects of low-level PAX6 haploinsufficiency in a dosage-sensitive manner.

A retrospective study of preimplantation embryos diagnosed with monosomy by fluorescence in situ hybridization (FISH).

This report is a retrospective study of preimplantation embryos diagnosed with monosomy for chromosomes 13, 15, 16, 18, 21, 22, X and Y on day 3 to determine the rate of true positives, false positives and/or mosaicism and to assess if these embryos are suitable for in vitro fertilization (IVF) transfer. In a one year period, 80 patients went through preimplantation genetic diagnosis for aneuploidy screening (PGD-AS). Monosomy was diagnosed in 51 embryos. Fluorescence in situ hybridization (FISH) was then performed on the blastomeres at day 5-7 with commercially available probes using the same probe set that initially identified monosomy for chromosomes 13, 16, 21 and 22 or chromosomes 15, 18, X and Y. Based on FISH analysis, the monosomy diagnosed during routine PGD-AS analysis was confirmed in 17 of the 51 embryos. A euploid result for the specific chromosomes tested was observed in 16 of the 51 embryos while mosaicism was found in the remaining 18 embryos. This results in an estimated false positive rate of 3.8% for a diagnosis of monosomy. Reanalysis of these embryos demonstrates that the majority of monosomy diagnoses represents true monosomy or mosaicism and should be excluded for transfer in IVF. Furthermore, improved understanding from recent emerging data regarding the fate of oocytes in women with advanced maternal age undergoing IVF to the development of early embryos may provide a valuable insight into the mechanism of chromosome mosaicism.