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Individuals with mosaic paternal uniparental disomy (UPD) of apparently all chromosomes have recently been described. They show a 46,XX karyotype, but with a mixture of normal biparental cells and cells entirely of paternal isodisomic origin. We describe an infant who primarily showed signs of Beckwith-Wiedemann syndrome (BWS), but also had other severe and eventually lethal medical problems, notably refractory hypoglycemia. We performed methylation studies for BWS, but incidentally for Angelman syndrome (AS) on leukocytes and in a skin FFPE sample. We also performed chromosome microarray [CNV and single-nucleotide polymorphism (SNP) array] on leukocytes. We found that the patient had hypomethylation consistent with both BWS and AS. Remarkably, this was due to mosaic paternal UPD for chromosomes 11 and 15, respectively. The SNP microarray showed mosaic paternal UPD for all chromosomes. Patients with unusual phenotypes for a typical imprinting disorder should be studied further with assays for imprinted loci on other chromosomes. Chromosomal SNP microarrays are useful in identifying patients with multiple UPDs, sometimes of the whole genome., (© 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

We describe a family with recurrent 11q23-qter deletion Jacobsen syndrome in two affected brothers, with unique mosaic deletion 'rescue' through development of uniparental disomy ( UPD) in the mother and one of the brothers. Inheritance studies show that the deleted chromosome is of maternal origin in both boys, and microarray shows a break near the ASAM gene. Parental lymphocyte chromosomes were normal. However, the mother is homozygous in lymphocytes for all loci within the deleted region in her sons, and presumably has UPD for this region. In addition, she is mosaic for the 11q deletion seen in her sons at a level of 20-30% in skin fibroblasts. We hypothesize that one of her #11 chromosomes shows fragility, that breakage at 11q23 occurred with telomeric loss in some cells, but 'rescue' from the deletion occurred in most cells by the development of mitotic UPD. She apparently carries the 11q deletion in her germ line resulting in recurrence of the syndrome. The older son is mosaic for the 11q cell line (70-88%, remainder 46, XY), and segmental UPD11 'rescue' apparently also occurred in his cytogenetically normal cells. This is a novel phenomenon restoring disomy to an individual with a chromosomal deletion. [ABSTRACT FROM AUTHOR]