Chromosome Ring 20 Syndrome

Chromosome Ring 20 syndrome is a rare chromosomal disorder characterized by medically hard to control epilepsy, nocturnal subtle seizures, behavioural problems and mild mental impairment. Unlike other chromosomal aberrations, typical appearances are rarely reported. Most cases there are no family members affected.

This syndrome is undoubtedly an under-diagnosed condition.  With cytogenetic chromosomal karyotyping in non-etiological cases of epilepsy, more cases of r(20) will undoubtedly be recognized.

It is speculated that an epigenetic mechanism disturbing the expression of genes close to the telomeric regions, rather than deletion of genes located at the distal 20p and/or 20q regions, may underlie the manifestation of r(20) syndrome.


Vignoli A, Bisulli F, Darra F, et al. 2016  Epilepsy in ring chromosome 20 syndrome. Epilepsy Res. 2016;128:83-93. doi:10.1016/j.eplepsyres.2016.10.004 

Unterberger I, Dobesberger J, Schober H, et al. 2019 A further case of familial ring chromosome 20 mosaicism - molecular characterization of the ring and review of the literature. Eur J Med Genet. 2019;62(11):103564. doi:10.1016/j.ejmg.2018.10.016

Giardino D, Vignoli A, Ballarati L, et al. 2010 Genetic investigations on 8 patients affected by ring 20 chromosome syndrome. BMC Med Genet. 2010;11:146. Published 2010 Oct 12. doi:10.1186/1471-2350-11-146 

Last modified
1 January 2021

ORPHA: 1444 Ring 20

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