The existence of parent of origin differences in the expression of some genes, a process known as genomic imprinting, has been recognised and documented over the past several years. This epigenetic marking process results in the differential expression of normal genes, depending on whether they are of maternal or paternal origin. A number of human disorders have been identified as resulting from alterations in genomic imprinting.1 One type of genetic abnormality which can unmask genomic imprinting is uniparental disomy (UPD), in which both chromosomes of one pair are inherited from one parent, with no contribution from the other.2 Distinct phenotypes exhibited by patients with maternal and paternal UPD(14) strongly suggest that at least some genes on human chromosome 14 are subject to imprinting effects.3-6 This finding is supported by studies in the mouse indicating that the distal portion of chromosome 12, recognised as a candidate imprinted region, is syntenic with human chromosome 14q.7 Nevertheless, no imprinted genes have yet been identified on chromosome 14, and the location of the imprinted region on human chromosome 14 remains unclear.

Analysis of parental origin effects in human trisomy for chromosome 14q8 or monosomy for the same chromosome9makes the region 14q23-q32 a candidate region for containing imprinted genes.10 Moreover, the observation of a partial duplication of 14q in a developmentally delayed girl with minor abnormalities and her phenotypically normal father led Robinet al 11 to propose that the 14q24.3-q31 region may be imprinted. As genotype-phenotype correlations in patients with aneusomy for this region may help the identification of imprinted genes on human chromosome 14, we report here a direct 14q31 duplication observed in a child with mild developmental delay and his phenotypically normal mother. This duplication was also detected in five relatives with a normal …