Constitutional mosaic genome-wide uniparental disomy due to diploidisation: an unusual cancer-predisposing mechanism

International audience; Molecular studies in a patient with Beckwith-Wiedemann syndrome phenotype who developed two different tumors revealed an unexpected observation of almost complete loss of heterozygosity of all chromosomes. We demonstrate, by means of numerous molecular methods that the absence of maternal contribution in somatic cells is due to high-degree (85%) genome-wide paternal uniparental disomy. Our observations indicate the genome-wide UPD results from diploidization, and have important implications for genetic counseling and tumor surveillance for the growing number of UPD-associated imprinting disorders.