We present the electroclinical features and cytogenetic findings of 2 siblings with the ring 20 chromosome (r(20)) phenotype, one of which had r(20) mosaicism. A history of epilepsy or learning problems should be determined in family members, although these relatives had no ring formation in chromosome 20. Whether the clinical features result from possible deletions or ring formation is discussed.
AtkinsLMillerWLSalamM. A ring-20 chromosome. J Med Genet. 1972;9(3):377–380.
2.
InoueYFujiwaraTMatsudaKRing chromosome 20 and nonconvulsive status epilepticus. A new epileptic syndrome. Brain. 1997;120(pt 6):939–953.
3.
KobayashiKInagakiMSasakiMSugaiKOthaSHashimotoT. Characteristic EEG findings in ring-20-syndrome as a diagnostic clue. Electroencephalogr Clin. Neurophysiol. 1998;107(4):258–262.
4.
VilleDKaminskaABahi-BuissonNEarly pattern of epilepsy in the ring chromosome 20 syndrome. Epilepsia. 2006;47(3):543–549.
5.
NishiwakiTHiranoMKumazawaMUenoS. Mosaicism and phenotype in ring chromosome 20 syndrome. Acta Neurol Scand. 2005;111(3):205–208.
6.
HerrgardEMononenTMervaalaEMore severe epilepsy and cognitive impairment in the offspring of a mother with mosaicism for the ring 20 chromosome. Epilepsy Res. 2007;73(1):122–128.
7.
Garcia-CruzDVasquezAIPerez-RulfoDRing-20-syndrome and loss of telomeric regions. Ann Genet. 2000;43(3-4):113–116.
8.
BackEVoiculescuYBrungerMWolffG. Familial ring (20) chromosomal mosaicism. Hum Genet. 1989;83:148–154.
9.
CaneviniMPSgroVZuffardiOChromosome 20 ring: a chromosomal disorder associated with a particular electroclinical pattern. Epilepsia. 1998;39(9):942–951.
10.
ZouYSVan DykeDLThorlandECMosaic ring 20 with no detectable deletion by fish analysis: characteristic seizure disorder and literature review. Am J Med Genet A. 2006;140(15):1696–1706.
11.
ElghezalHHannachiHMougouSKammounHTrikiCSaadA. Ring chromosome 20 syndrome without deletions of the subtelomeric and CHRNA4-KCNQ2 genes loci. Eur J Med Genet. 2007;50(6):441–445.
12.
ShafferLGSlovakMLCampbellLJ (eds); ISCN, An International System for Human Cytogenetic Nomenclature. Basel, Switzerland: S.Karger; 2009.
13.
FrynsJKleczkowskaADecockP, Massa G, van den Berghe H. 46XX/46XX del(20)(pter->p12.2) mosaicism limited to fibroblasts associated with MCA/MR and severe growth deficit. Ann Genet. 1992;35(4):234–236.
14.
AdeyinkaAAdamsSALorentzCPVan DykeDLJalalSM. Subtelomere deletions and translocations are frequently familial. Am J Med Genet. 2005;135(1):28–35.
15.
ConlinLKKramerWHutchinsonALMolecular analysis of ring chromosome 20 syndrome reveals two distinct groups of patients. J Med Genet. 2011;48(1):1–9.
16.
VillégaFNgayapHEspil-TarisCPolymorphic expression of epilepsy and cognitive impairment in ring chromosome 20 syndrome. Arch Pediatr. 2011;18(4):394–396.
