P05.01: Chromosomal microarray: beyond copy number variations: Poster discussion hub abstracts

Chromosomal microarray analysis (CMA) is the modality of choice for prenatal diagnosis when fetal malformations are found. Microdeletion/microduplication syndromes diagnosed by CMA contribute to the diagnostic rate, beyond that of chromosomal analysis, by 3-8%. However, the CMA platform can also provide diagnoses of monogenic diseases, imprinting disorders and uniparental disomy (UPD). Three unrelated expectant couples underwent amniocentesis for varying reasons: IUGR, very abnormal maternal serum analytes, and patient's request. Fetal genomic DNA was extracted from amniocytes and high resolution CMA analysis was performed using Affymetrix CytoScan array. CMA analysis revealed a microdeletion of 75kbp encompassing the BLM gene in the IUGR fetus. Further investigation established a fetal diagnosis of Bloom syndrome upon observation of maternal deletion of one allele of the gene and paternal founder Ashkenazi mutation on the other fetal allele. A 14q32.2q32.31deletion encompassing 3.4-Mbp was found in the fetus referred following a finding of abnormal maternal serum analytes. Further SNP analysis indicated that the deleted segment originated from the maternal copy of chromosome 14, leading to the diagnosis of Kagami Ogata syndrome, an imprinting disorder. The figure shows the dysplastic corpus callosum, placentomegaly, DV agenesis draining to IVC, and CMA results of this case. The third fetal CMA, performed at parental request, revealed maternal UPD of most of chromosome 11q without any clear clinical significance. Comprehensive CMA analysis including both platforms of oligo and SNP array may establish the diagnosis of a spectrum of disorders that is much broader than copy number variations. Supporting information can be found in the online version of this abstract Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.