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Uniparental disomy - clinical consequences due to imprinting and activation of recessive genes

Uniparental disomy (UPD) is often considered as an event to be characterized exclusively by molecular genetic or epigenetic approaches. Still in at least one third of cases UPD emerge in connection with or due to a chromosomal rearrangement.

Till date ~2,500 UPD cases detected in clinical, non-tumor cases are reported in the literature ( Based on this, the presently known imprinting syndromes, chromosomal contribution to UPD phenomenon, and cytogenetic subgroups of UPD and segmental UPD are reviewed.

UPD may arise in clinical cases, as well as it may be exclusively tumor related. For clinical cases imprinting is quantitatively the most important problem. Still isodisomy may also be a problem, due to “activation” of recessive mutation-events, thus inducing rare autosomal recessive disorders.

Overall, as UPD is more but an interesting rarity, the genetic background of each "UPD-patient" needs to be characterized besides by molecular methods, also by molecular cytogenetics in detail.

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Correspondence to Thomas Liehr.

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This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The Creative Commons Public Domain Dedication waiver ( applies to the data made available in this article, unless otherwise stated.

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Liehr, T. Uniparental disomy - clinical consequences due to imprinting and activation of recessive genes. Mol Cytogenet 7 (Suppl 1), I21 (2014).

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  • Genetic Background
  • Clinical Consequence
  • Clinical Case
  • Molecular Method
  • Chromosomal Rearrangement