Carriers of either homologous or non-homologous acrocentric rearrangements are 
at an increased risk for aneuploidy, and, thus, for uniparental disomy (UPD). 
Abnormal phenotypes due to genomic imprinting are associated with UPD for the 
acrocentric chromosomes 14 and 15. The purpose of this study was to determine 
the prevalence of UPD in a population with acrocentric rearrangements (either an 
isochromosome or a Robertsonian translocation) and abnormal phenotypes. Fifty 
individuals were studied. Of the 50 rearrangements, two were homologous 
rearrangements and both showed UPD. Forty-eight were non-homologous Robertsonian 
translocations, of which two showed UPD. This study demonstrates that UPD 
explains the abnormal phenotypes in some balanced carriers of acrocentric 
rearrangements. Our results and the large number of case reports in the 
literature suggest that patients with abnormal phenotypes and acrocentric 
rearrangements of chromosomes 14 or 15 should be tested for UPD.