Maternal UPD 20 in an infant from a pregnancy with mosaic trisomy 20

Maternal uniparental disomy (UPD) 20 was found in a 35-month-old girl, the product of a pregnancy complicated by a prenatal diagnosis of mosaic trisom y 20. Phenotypic abnormalities included pre- and postnatal growth failure, microcephaly, minor dysmorphic features and psychomotor developmental delay . Chromosomal analysis on cord blood revealed only a normal 46,XX karyotype . Microsatellite analysis of 27 chromosome 20 loci confirmed maternal UPD f or all 11 informative markers. Maternal heterodisomy was detected in two an d maternal isodisomy in three loci. In the remaining six loci, a non-inform ative maternal UPD pattern was displayed, as mother and proband are homozyg ous for the same allele. To our knowledge this is the first reported case o f maternal disomy 20 with normal karyotype ascertained by a mosaic trisomy 20 pregnancy. Copyright (C) 2001 John Wiley & Sons, Ltd.