Many people with ring chromosome 21 have normal development and are healthy, having been diagnosed after having chromosome testing due to infertility, multiple miscarriages, or a child with a chromosome abnormality. Ring chromosome 21 is a rare chromosome abnormality in which the ends of chromosome 21 join together to form a ring shape. Epilepsy responds to vagus nerve stimulation in ring chromosome 20 syndrome. Autosomal ring chromosomes in human genetic disorders. Ring chromosome 20 is a chromosome abnormality that affects the development and function of the brain.
The clinical limits of this syndrome can now be defined. The syndrome is associated with epileptic seizures, behaviour disorders and mental retardation when not all cells contain a ring chromosome 20, the individual suffers from ring 20. A study of ring 20 chromosome karyotype with epilepsy. Ring chromosome 21 genetic and rare diseases information. Ring chromosomes were first discovered by lilian vaughan morgan in 1926. Ring chromosomes can extend those design principles to provideamodelfor genomicrearrangement, ring chromosome evolution,andhumanringchromosome disorders. Ring chromosome 20 syndrome a rare chromosomal cause of.
Molecular analysis of ring chromosome 20 syndrome reveals. New association between ring chromosome 20 syndrome. Twentyfive cases of ring 20 chromosome karyotypes including this case have been reported in the literature. Ring chromosome 20 epilepsy syndrome in children neurology. Ring chromosome 20 syndrome is a rare chromosomal disorder characterized by refractory epilepsy, with seizures in wakefulness and sleep, behavioral problems and mild to severe cognitive impairment. Ring chromosome 20 syndrome is a rare cause of refractory epilepsy a patient who present with intractable epilepsy with frontal epileptiform discharges, mental developmental delay, without dysmorphic features should be suspected of chromosomal abnormalities especially ring chromosome 20. Ring chromosome 20 genetic and rare diseases information.
Six cases of epilepsy associated with ring chromosome 20 are presented. The study of these cases and 20 cases reported in the literature revealed that they constitute a distinct epileptic syndrome. Ring chromosomes involving both the autosomes and the sex chromosomes have been described pezzolo et al. Ring 20 syndrome ring 20 syndrome is a very rare condition in which one of the two copies of chromosome 20 has formed a ring rather than the typical linear chromosome structure. They are heterogeneous with variable size and genetic content and can originate from any chromosome.
Ring chromosome 20 syndrome genetics home reference nih. Ring chromosome 20, ring shaped chromosome 20 or r 20 syndrome is a rare human chromosome abnormality where the two arms of chromosome 20 fuse to form a ring chromosome. The ring chromosome 20 r20 syndrome represents the most striking example of a chromosomal aberration in which epilepsy can be the only expression of. The potassium channelecoding gene kcnq2 is localized at the locus q. Deletion of chromosome 21 disturbs human brain morphogenesis. Pdf purpose the purpose of this paper is to discuss the challenges of. In some people, the ring chromosome 20 is found in every cell in the body, whereas in others, it is only seen in a. A link between epilepsy onset and neuropsychological impairment in three children. Background the ring chromosome 20 syndrome r20 is a rare genetic disorder associated with a refractory electroclinical epilepsy syndrome and variably expressed comorbidities of intellectual disability and dysmorphism. Ring chromosome 20 syndrome genetics home reference.
Facial dysmorphism or other congenital malformations are rarely reported making it difficult to diagnose the syndrome based on clinical findings alone. Media in category ring chromosome 20 syndrome this category contains only the following file. Ring chromosome 20 syndrome rc20 is one of a number of chromosomal disorders associated with difficult to control epilepsy. There are several different forms of the r 20 syndrome, with potential differences among. Work is ongoing to determine how the presence of a ring chromosome. It is due to an abnormality in chromosome number 20. Pdf assessing the role of ketogenic dietary therapy in ring. Request pdf ring chromosome 20 the causal disease definitions ring chromosome 20 is a rare chromosomal abnormality and a rare cause of intractable epilepsy. Ring chromosomes arise following breakage and rejoining in both chromosome arms. Why the formation of the ring causes epilepsy and other symptoms of the syndrome is not well understood.
Many of the patients showed growth retardation and minor malformations. Ring chromosome 20 r20 syn drome is one of the chromosomal abnormalities almost always asso ciated with epilepsy ville et al. Chromosome 21 ring is a rare chromosomal disorder in which the affected infant has a breakage of chromosome 21 at both ends, and the ends of the chromosome join together to form a ring. All human chromosomes can form a ring chromosome, although they are all very rare, with a combined incidence of only one in 30. Chromosomes are very important structures within each cell in the body, which hold our genetic material. Abstract we present the clinical, electroencephalographic, neuroimaging brain magnetic resonance image mri and spectroscopy by mri and cytogenetic findings of a young male patient with a rare. Department of clinical genetics, university hospital, se221 85, lund, sweden december 2001 chromosomes are often regarded merely as static containers for genetic information. Ring 21 ftnw understanding rare chromosome and gene. Often, the ring chromosome is present in only some of a persons cells. More than 30 cases have been described in the literature since 1976. Other symptoms might include intellectual disability, behavioral difficulties, growth delay, short stature, a small head microcephaly, and characteristic facial features. Ring chromosome 20 syndrome with intractable epilepsy.
The seizures may occur during the day or at night during sleep. The number of cases reported in literature is less than 100, though we suspect that there are many more cases diagnosed or undiagnosed with this extremely rare. A ring chromosome typically occurs as a random event during the formation of reproductive cells eggs or sperm or in early embryonic development. Pdf epilepsy responds to vagus nerve stimulation in ring. Ring chromosome 20 and nonconvulsive status epilepticus.
Synthetic biology perfect designer chromosome v and. Ring chromosome 20 syndrome is a condition that affects the normal development and function of the brain. Ring chromosome 20 ring chromosome 20 is one of the most frequent forms of ring chromosomes. Mechanisms of ring chromosome formation in 11 cases of human ring chromosome 21. Ring chromosome 20 is a genetic syndrome characterized by a childhood or adolescentonset epileptic encephalopathy in a previously developmentally normal child.
More than 50% of all patients 731 have mosaicism with a normal clone. Guideline recommendations for diagnosis and clinical. A ring chromosome is formed by the fusion of two arms of a straight chromosome during prenatal before birth development. Almost half of the people with ring 21 chromosomes described in the medical literature are healthy and develop normally. Ring chromosome 20 syndrome, also known as r 20, is a rare chromosomal anomaly resulting from a break on each arm of chromosome 20 resulting in ring formation. Marleide da mota gomes 1, irene lucca 2, sonia alonso monteiro bezerra 2, juan llerena jr 3, denise madeira moreira 1. However,noassociationwith ring chromosome 20 was previously described, to the best of our knowledge.
Ring chromosome 20 syndrome is caused by a chromosomal abnormality known as a ring chromosome 20 or r 20. Article abstract ring chromosome 20 mosaicism is associated with dysmorphic features, mental retardation, and intractable seizures, including recurrent episodes of nonconvulsive status epilepticus. In individuals with chromosome 22 ring, associated symptoms and findings may be extremely variable, depending upon the amount and location of genetic material lost from the 22nd chromosome, the stability of the ring chromosome during subsequent cellular divisions i. A ring chromosome is an aberrant chromosome whose ends have fused together to form a ring. In the remaining cells, 4% showed 47 chromosomes with double rings and 6% showed structurally abnormal rings presumably derived from the original r 20 pq. Methods to understand the structure and composition of the ring chromosome 20 r 20 in this patient cohort, blood specimens. Allison watson and don gordon at the launch of ring20 research and support uk. Wechemicallysynthesized,assembled,andincorporateddesignerchromosomesynv536,024base pairs of s. Very often, chromosome abnormalities give rise to specific physical symptoms, however, the severity of these can vary from individual to individual. The ring 20 syndrome is associated with a high incidence of epilepsy, particularly partial epilepsy. People with ring chromosome 20 often have recurrent seizures or epilepsy. Nonpharmacological treatments alongside antiepileptic drugs early after diagnosis may help reduce seizure frequency and preserve cognition. Currently, based on variability in phenotypes of different ring chromosomes, there is limited support for the existence of a ring syndrome 8,17e21. Ring chromosome 20 syndrome a rare chromosomal cause of refractory epilepsy in children.
Assessing the role of ketogenic dietary therapy in ring. C band investigation revealed presence of a monocentric ring in all 100 analysed. Disorders arising from the formation of a ring chromosome include ring chromosome 20 syndrome where a ring formed by one copy of chromosome 20 is associated with epilepsy. Phenotypes associated with ring chromosomes are highly variable as apart from any deletion caused by ring formation, imbalances from ring instability can also occur. You can use this leaflet and any of the media listed in do. Ring chromosome 20 with ncse is a rare but distinctive epileptic syndrome. A study of the ring chromosome syndrome is presented with detailed clinical and cytogenetic features of three new unrelated cases. Ring chromosome 20 syndrome is a rare epilepsy syndrome, affecting a very small number of people worldwide. People with ring chromosome 20 syndrome have one copy of this abnormal chromosome in some or all of their.
A rare epileptic syndrome of ring chromosome 20 with non. Ring 21 ring 21 is a rare genetic condition caused by having a ring shaped chromosome. Chromosomal abnormalities occur when there is a defect in a chromosome, or in the arrangement of the genetic material on the chromosome. A ring chromosome is a circular structure that occurs when a chromosome breaks in two places and its broken ends fuse together. Ring chromosome 14 syndrome is a rare chromosomal disorder characterized by early onset refractory epilepsy, intellectual disability, autism spectrum disorder and a number of diverse health issues. Chromosome 22 ring nord national organization for rare. An analysis of these cases together with those in the literature indicates that the syndrome forms a continuous spectrum, and no further taxonomic subdivision is possible at. In some people, the ring chromosome 20 is found in every cell in the body, whereas in others, it is only seen in a percentage of cells, with the remaining cells having two normal chromosome 20s. A ring chromosome is denoted by the symbol r in human genetics and r in drosophila genetics. Chromosome 21 ring nord national organization for rare. Ring chromosome 20 syndrome is almost never inherited.
Although still considered rare, r 20 syndrome is being increasingly diagnosed. The vast majority of patients with ring chromosome 20 are. Ring chromosome 20 syndrome is a rare chromosomal disease characterized by mental retardation, behavioral problems, unspe. Ring chromosome 20 r 20 syndrome is a welldefined chromosomal disorder characterized by epilepsy, mildtomoderate mental retardation, and lack of recognizable dysmorphic features. Ring chromosome 20 syndrome is a rare chromosomal disorder characterized by refractory epilepsy, with seizures in wakefulness and sleep. Ring chromosome 20 r 20 syndrome is characterized by mild to moderate learning disability, behavioural disorders, epilepsy, and various dysmorphic features. Ring chromosome 20 r20 is a rare chromosomal disorder, first. Pdf psychosis and epilepsy in ring chromosome 20 syndrome. There are at least 1 reported patients with this abnormality. Ring chromosomes may form in cells following genetic damage by mutagens like radiation, but they may also arise. Enable javascript to view the expandcollapse boxes. Their unusual chromosomes are discovered by chance, during tests for infertility or after.
Each human being has 23 pairs of chromosomes 46 in total. People with ring chromosome 20 syndrome have one copy of this abnormal chromosome in some or all of their cells. Life with r20ring chromosome 20 syndrome watson 2015. Ring chromosome 20 r20 is a rare condition and one that often causes epilepsy in children. The amount of genetic material lost at the two ends of the chromosome may vary. The most common feature of this condition is recurrent seizures epilepsy in childhood. It is one of the more commonly seen ring chromosomes.
The ring chromosome 20 foundation was created to provide information, resources and assistance to families affected by ring chromosome 20 syndrome. Electroclinical evolution in ring chromosome 20 epilepsy. Mcginniss mj, kazazian hh jr, stetten g, petersen mb et al. Our hope is to share as much information as possible so that medical professionals, physicians, and families can better understand the syndrome and its treatment.
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