MICRODELETION AND MICRODUPLICATION SYNDROMES

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Description

Scientific background

With the advancement of high-resolution techniques and fluorescence in situ hybridization (FISH), an increasing number of clinical syndromes have been found to be caused by microdeletions. Microdeletion syndromes usually lead to complex yet clinically distinguishable phenotypes. They usually occur sporadically as an isolated case in the family. Most of the chromosomal microdeletion syndromes that are based on loss of mostly submicroscopic chromosomal segments are associated with mental retardation. However, other symptoms such as specific combinations of malformations and/or dysmorphic signs and characteristic “behavioral phenotypes” are almost always prominent. In these cases, there is usually a suspected clinical diagnosis that requires a specific examination. Some of the microdeletion syndromes belong to the more common genetic disorders, especially the microdeletion 22q11.2 which causes the DiGeorge syndrome is observed with a frequency of at least 1:4,000. Most of the microdeletion syndromes are also called contiguous gene syndromes as the symptoms are most likely caused by the loss of several genes located in the deleted region.

An overview of some important microdeletion syndromes which are regularly analyzed is listed below. Some of the syndromes mentioned may also have other causes (single gene mutation e.g. in AS and / or UPD e.g. in PWS and AS).

 

Classic microdeletion syndromes:

  • Angelman syndrome (15q11-q13)
  • Cri-du-chat syndrome (5p15.2-p15.3)
  • DiGeorge syndrome (22q11.2)
  • Miller-Dieker syndrome (17p13.3)
  • Prader-Willi syndrome (15q11-q13)
  • Shprintzen syndrome (22q11.2)
  • Smith-Magenis syndrome (17p11.2)
  • Williams-Beuren syndrome (7q11.23)
  • Wolf-Hirschhorn syndrome (4p16.3)

 

The use of chromosomal microarrays (CMA) has identified numerous new microdeletion and duplication syndromes which were unknown a few years ago and whose phenotype was only recognized as characteristic after repeated description of the same imbalance.

 

Newer microdeletion and duplication syndromes with mental retardation (MR) as a leading symptom:

  • Microdeletion 1q21.1
  • Microduplication 1q21.1
  • Microdeletion 1p36
  • Microdeletion 1q41q42
  • Microdeletion 2p15p16.1
  • Microdeletion 3q29
  • Microduplication 7q11.23
  • Microdeletion 9q22.3
  • Microdeletion/duplication 10q11.21-q11.23
  • Microdeletion 12q14
  • Microdeletion 14q11.2
  • Microdeletion 15q11.2 (Burnside-Butler syndrome)
  • Microdeletion 15q13.3
  • Microdeletion 15q24 (Witteveen-Kolk syndrome)
  • Microdeletion/duplication 16p11.2
  • Microdeletion 16p11.2p12.2
  • Microdeletion 16p13.1
  • Microduplication 16p13.1
  • Microduplication 17p11.2 (Potocki-Lupski syndrome)
  • Microdeletion 17q21.31 (Koolen-De Vries syndrome)
  • Microdeletion 19q13.11
  • Distal microdeletion 22q11.2
  • Microduplication 22q11.2
  • Microduplication Xq28

 

Lists modified from Vissers L. et al, J Med Genet 47: 289 (2010), Slavotinek AM, Hum Genet 124:1 (2008) and Watson et al, Annu Rev Genome Hum Genet 15:215 (2014).

 

References

Goldenberg P 2018, Pediatr Ann 47(5):e198 / Vissers et al. 2010, J Med Genet 47:289 / Slavotinek 2008, Hum Genet 124:1/ Rost and Klein 2005, J Lab Med 29:152 / Seller et al. 2002, Clin Dysmorphol 11:113 / Dekeersmaker et al. 2002, Prenat Diagn 22:366 / Rost 2000, Monatsschr Kinderheilkd 148:55

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