A further case of familial ring chromosome 20 mosaicism - molecular characterization of the ring and review of the literature

Iris Unterberger; Judith Dobesberger; Harald Schober; Birgit Krabichler; Claudia Lamina; Ulrich Schatz; Johannes Zschocke; Gerhard Luef; Dieter Kotzot; Christine Fauth

doi:10.1016/j.ejmg.2018.10.016

A further case of familial ring chromosome 20 mosaicism - molecular characterization of the ring and review of the literature

Eur J Med Genet. 2019 Nov;62(11):103564. doi: 10.1016/j.ejmg.2018.10.016. Epub 2018 Oct 29.

Authors

Affiliations

¹ Department of Neurology, Innsbruck Medical University, Anichstraße 35, A-6020 Innsbruck, Austria.
² Department of Neurology, Innsbruck Medical University, Anichstraße 35, A-6020 Innsbruck, Austria; Department of Neurology, Christian Doppler Klinik, Paracelsus Medical University of Salzburg, Ignaz-Harrer-Straße 79, A-5020 Salzburg, Austria.
³ Department of Pediatrics, Landeskrankenhaus Feldkirch, Carinagasse 47, A-6807 Feldkirch, Austria.
⁴ Division of Human Genetics, Department of Medical Genetics, Molecular and Clinical Pharmacology, Innsbruck Medical University, Peter-Mayr-Straße 1, A-6020 Innsbruck, Austria.
⁵ Division of Genetic Epidemiology, Department of Medical Genetics, Molecular and Clinical Pharmacology, Innsbruck Medical University, Schöpfstraße 41, A-6020 Innsbruck, Austria.
⁶ Division of Human Genetics, Department of Medical Genetics, Molecular and Clinical Pharmacology, Innsbruck Medical University, Peter-Mayr-Straße 1, A-6020 Innsbruck, Austria. Electronic address: Christine.fauth@i-med.ac.at.

PMID: 30385235
DOI: 10.1016/j.ejmg.2018.10.016

Abstract

Ring chromosome 20 syndrome is a rare chromosomal disorder characterized by childhood-onset drug-resistant epilepsy, behavioral problems and variable cognitive impairment. While most cases occur sporadically, parent-to-child transmission of ring 20 mosaicism has only been reported in a few exceptional families. We identified a further family with mother-to-child transmission of ring 20 mosaicism. Detailed characterization of the ring chromosome showed a complete ring with preserved telomere repetitive sequences. SNP genotyping excluded mosaic uniparental disomy and indicated that the chromosome was transmitted without recombination from mother to child. These results corroborate the findings of a previous study and support the hypothesis that inherited mosaicism is due to transmission of an unstable chromosome either prone to ring opening or to ring re-formation.

Keywords: Inherited mosaicism; Ring chromosome 20 syndrome; Ring formation.

MeSH terms

Adolescent
Adult
Age of Onset
Child
Chromosomes, Human, Pair 20 / genetics*
Epilepsy / drug therapy
Epilepsy / genetics*
Epilepsy / pathology
Female
Humans
In Situ Hybridization, Fluorescence
Infectious Disease Transmission, Vertical
Male
Mosaicism
Phenotype
Ring Chromosomes*
Young Adult

Supplementary concepts

Ring Chromosome 20 Syndrome