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Peron A, Catusi I, Recalcati MP, Calzari L, Larizza L, Vignoli A, Canevini MP. Ring Chromosome 20 Syndrome: Genetics, Clinical Characteristics, and Overlapping Phenotypes. Front Neurol 2020; 11:613035. [PMID: 33363513 PMCID: PMC7753021 DOI: 10.3389/fneur.2020.613035] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2020] [Accepted: 11/09/2020] [Indexed: 12/15/2022] Open
Abstract
Ring chromosome 20 [r(20)] syndrome is a rare condition characterized by a non-supernumerary ring chromosome 20 replacing a normal chromosome 20. It is commonly seen in a mosaic state and is diagnosed by means of karyotyping. r(20) syndrome is characterized by a recognizable epileptic phenotype with typical EEG pattern, intellectual disability manifesting after seizure onset in otherwise normally developing children, and behavioral changes. Despite the distinctive phenotype, many patients still lack a diagnosis-especially in the genomic era-and the pathomechanisms of ring formation are poorly understood. In this review we address the genetic and clinical aspects of r(20) syndrome, and discuss differential diagnoses and overlapping phenotypes, providing the reader with useful tools for clinical and laboratory practice. We also discuss the current issues in understanding the mechanisms through which ring 20 chromosome causes the typical manifestations, and present unpublished data about methylation studies. Ultimately, we explore future perspectives of r(20) research. Our intended audience is clinical and laboratory geneticists, child and adult neurologists, and genetic counselors.
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Affiliation(s)
- Angela Peron
- Human Pathology and Medical Genetics, ASST Santi Paolo e Carlo, San Paolo Hospital, Milan, Italy.,Child Neuropsychiatry Unit - Epilepsy Center, Department of Health Sciences, ASST Santi Paolo e Carlo, San Paolo Hospital, Università Degli Studi di Milano, Milan, Italy.,Division of Medical Genetics, Department of Pediatrics, University of Utah School of Medicine, Salt Lake City, UT, United States
| | - Ilaria Catusi
- Laboratory of Cytogenetics and Molecular Genetics, Istituto Auxologico Italiano IRCCS-Istituto di Ricovero e Cura a Carattere Scientifico, Cusano Milanino, Milan, Italy
| | - Maria Paola Recalcati
- Laboratory of Cytogenetics and Molecular Genetics, Istituto Auxologico Italiano IRCCS-Istituto di Ricovero e Cura a Carattere Scientifico, Cusano Milanino, Milan, Italy
| | - Luciano Calzari
- Bioinformatics and Statistical Genomics Unit, Istituto Auxologico Italiano IRCCS-Istituto di Ricovero e Cura a Carattere Scientifico, Cusano Milanino, Milan, Italy
| | - Lidia Larizza
- Laboratory of Cytogenetics and Molecular Genetics, Istituto Auxologico Italiano IRCCS-Istituto di Ricovero e Cura a Carattere Scientifico, Cusano Milanino, Milan, Italy
| | - Aglaia Vignoli
- Child Neuropsychiatry Unit - Epilepsy Center, Department of Health Sciences, ASST Santi Paolo e Carlo, San Paolo Hospital, Università Degli Studi di Milano, Milan, Italy
| | - Maria Paola Canevini
- Child Neuropsychiatry Unit - Epilepsy Center, Department of Health Sciences, ASST Santi Paolo e Carlo, San Paolo Hospital, Università Degli Studi di Milano, Milan, Italy
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A further case of familial ring chromosome 20 mosaicism - molecular characterization of the ring and review of the literature. Eur J Med Genet 2018; 62:103564. [PMID: 30385235 DOI: 10.1016/j.ejmg.2018.10.016] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2018] [Revised: 08/24/2018] [Accepted: 10/28/2018] [Indexed: 11/22/2022]
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.
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Gago-Veiga AB, Toledano R, García-Morales I, Pérez-Jiménez MA, Bernar J, Gil-Nagel A. Specificity of electroclinical features in the diagnosis of ring chromosome 20. Epilepsy Behav 2018; 80:215-220. [PMID: 29414555 DOI: 10.1016/j.yebeh.2017.12.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/11/2017] [Revised: 12/01/2017] [Accepted: 12/01/2017] [Indexed: 10/18/2022]
Abstract
BACKGROUND Ring chromosome 20 (R20) syndrome is a chromosomal disorder characterized mainly by drug-resistant frontal lobe seizures, recurrent nonconvulsive status epilepticus (NCSE), and typical EEG features. The aim of this study was to investigate if this triad is common and specific to all patients with R20. METHODS In this cross-sectional study (from 2000 to 2011), we selected patients who fulfilled at least two out of three criteria: drug-resistant frontal lobe seizures, recurrent NCSE, and characteristic electroencephalography (EEG) features. In all patients, diagnosis was based on karyotype analysis of at least 100 metaphases. RESULTS We identified 36 patients who met at least two of the selected criteria: six patients (16.7%) with R20 and 30 (83.3%) without R20 (non-R20). All patients with R20 met all three criteria. Eleven (36.7%) patients without R20, however, also displayed the full triad. In 19 patients without R20 (63.3%), one of the three clinical features was missing: frontal lobe seizures were not resistant to antiepileptic drugs (AED) in four (13.3%), recurrent NCSE was missing in six (20%), and nine (30%) patients did not have typical EEG features. Based on this data, specificity was 63.3%, positive predictive value was 35.3%, and sensitivity and negative predictive values were 100%. Additionally, a review of all publications describing the R20 phenotype revealed that 81.98% of patients with R20 display the full electroclinical triad. CONCLUSIONS In our study, all patients with R20 displayed the three electroclinical characteristics. This is in line with previous reports (presenting high sensitivity and negative predictive value). However, these features can also be observed in other epilepsies and are not specific to R20. Our findings suggest that in the presence of the full triad of symptoms, karyotype analysis focused on chromosome 20 should be conducted.
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Affiliation(s)
- A B Gago-Veiga
- Epilepsy Unit, Department of Neurology, Hospital Universitario de La Princesa, Diego de León 62, 28006 Madrid, Spain
| | - R Toledano
- Epilepsy Program, Department of Neurology, Hospital Ruber International, La Masó 38, 28034 Madrid, Spain
| | - I García-Morales
- Epilepsy Program, Department of Neurology, Hospital Ruber International, La Masó 38, 28034 Madrid, Spain
| | - M A Pérez-Jiménez
- Epilepsy Monitoring Unit, Clinical Neurophysiology Department, Niño Jesús Pediatric University Hospital, Menendez Pelayo 65, 28009 Madrid, Spain
| | - J Bernar
- Department of Genetics, Hospital Ruber International, La Masó 38, 28034 Madrid, Spain
| | - A Gil-Nagel
- Epilepsy Program, Department of Neurology, Hospital Ruber International, La Masó 38, 28034 Madrid, Spain.
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Nishikawa K, Itoi F, Nagahara M, Jose M, Matsunaga A, Ueda J, Iwamoto T. The normality of sperm in an infertile man with ring chromosome 15: a case report. J Assist Reprod Genet 2018; 35:251-256. [PMID: 29063501 PMCID: PMC5845033 DOI: 10.1007/s10815-017-1061-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2017] [Accepted: 10/05/2017] [Indexed: 10/18/2022] Open
Abstract
PURPOSE The purpose of this report is to analyze the chromosome status and fertilization capability of sperm obtained from an infertile male patient with ring chromosome 15. METHODS This was a case report at a private in vitro fertilization clinic. A man diagnosed with severe oligozoospermia carrying ring chromosome 15. To evaluate the chromosome status and fertilization capability, sperm from a patient carrying ring chromosome 15 were injected into enucleated mouse oocytes. RESULTS The karyotypes of motile sperm from a patient carrying ring chromosome 15 were normal, and ring chromosome 15 was not observed in the chromosome spread samples of 1PN. In addition, these motile sperm retained the fertilization capability. However, the fertilization rates decreased (85.2, 76.2, and 64.3%, respectively) along with the decline of the aspect ratio of the sperm head (≥ 1.50, 1.30-1.49, and < 1.30, respectively). CONCLUSIONS The karyotypes were normal without ring chromosome 15, and motile sperm with a high aspect ratio showed adequate potential for fertilization.
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Affiliation(s)
- Kazuyo Nishikawa
- Department of Infertility, Green Bell Clinic, Kitamachi 2-160, Toyota, Aichi, 471-0027, Japan
- Department of Infertility, Royal Bell Clinic, Midori-ku, Nagoya, Aichi, 458-0801, Japan
| | - Fumiaki Itoi
- Department of Infertility, Green Bell Clinic, Kitamachi 2-160, Toyota, Aichi, 471-0027, Japan.
| | - Miki Nagahara
- Center for Education in Laboratory Animal Research, Chubu University, Kasugai, Aichi, 487-8501, Japan
| | - Mami Jose
- Center for Education in Laboratory Animal Research, Chubu University, Kasugai, Aichi, 487-8501, Japan
| | - Ayumi Matsunaga
- Center for Education in Laboratory Animal Research, Chubu University, Kasugai, Aichi, 487-8501, Japan
| | - Jun Ueda
- Center for Education in Laboratory Animal Research, Chubu University, Kasugai, Aichi, 487-8501, Japan.
- Center for Advanced Research and Education, Asahikawa Medical University, Asahikawa, Hokkaido, 078-8510, Japan.
| | - Takashi Iwamoto
- Center for Education in Laboratory Animal Research, Chubu University, Kasugai, Aichi, 487-8501, Japan
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Abstract
Ring chromosomes arise following breakage and rejoining in both chromosome arms. They are heterogeneous with variable size and genetic content and can originate from any chromosome. Phenotypes associated with ring chromosomes are highly variable as apart from any deletion caused by ring formation, imbalances from ring instability can also occur. Of interest is ring chromosome 20 which has a significant association with epilepsy with seizure onset in early childhood. Severe growth deficiency without major malformations is a common finding in the ring chromosome carrier. This phenotype associated with ring behaviour and mitotic instability and independent of the chromosome involved has been termed the "ring syndrome". Precise genotype-phenotype correlations for ring chromosomes may not be possible as influencing factors vary depending on the extent of deletion in ring formation, ring instability and the level of mosaicism. Although ring chromosomes usually arise as de novo events, familial transmission of rings from carrier to offspring has been described and prenatal diagnosis for any pregnancies should always be considered.
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Affiliation(s)
- Moh-Ying Yip
- SEALS Genetics Laboratory, NSW Health Pathology, Prince of Wales Hospital, Randwick, Sydney, NSW 2031, Australia
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Tezer FI, Aktas D, Alikasifoglu M, Saygi S. Two siblings with similar phenotypes: one of them had ring 20 chromosome. Clin EEG Neurosci 2013. [PMID: 23188914 DOI: 10.1177/1550059412451700] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
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.
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Affiliation(s)
- F Irsel Tezer
- Department of Neurology, Hacettepe University, Ankara, Turkey.
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Gahr M, Kerling F, Ludolph A, Plener P. Cognitive impairment and abnormal behaviour related to ring chromosome 20 aberration. J Autism Dev Disord 2012; 42:1146-8. [PMID: 21858587 DOI: 10.1007/s10803-011-1346-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Elens I, Vanrykel K, De Waele L, Jansen K, Segeren M, Van Paesschen W, Ceulemans B, Boel M, Frijns JP, Buyse G, Lagae L. Ring chromosome 20 syndrome: electroclinical description of six patients and review of the literature. Epilepsy Behav 2012; 23:409-14. [PMID: 22424860 DOI: 10.1016/j.yebeh.2012.02.008] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/17/2011] [Revised: 02/06/2012] [Accepted: 02/07/2012] [Indexed: 12/20/2022]
Abstract
BACKGROUND Ring chromosome 20 syndrome is a rare chromosomal disorder. METHODS In six patients, we focused on the presenting epileptic phenotype, the behavioral and mental problems and the relationship between the ratio of mosaicism and the age at onset of the epilepsy. RESULTS All patients presented with pharmacoresistant frontal lobe complex partial seizures. The earliest onset of epilepsy was seen in patients without mosaicism. There were three patients out of six with behavioral disturbances before the onset of seizures. All patients had mild to moderate cognitive impairment. Electroencephalogram recordings showed rhythmic theta waves with frontal predominance and non-convulsive status epilepticus (NCSE). CONCLUSIONS The ring chromosome 20 syndrome is characterized by childhood-onset refractory epilepsy continuing throughout adult life, mental disability, and behavioral disturbances which can originate before seizure onset. Ictal EEG reveals a unique pattern. Our findings indicate a possible link between the percentage of affected cells and the age of epilepsy onset.
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Affiliation(s)
- Iris Elens
- Department of Paediatric Neurology, University Hospital Leuven, Belgium
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The evolving electroclinical syndrome of "epilepsy with ring chromosome 20". Seizure 2011; 21:92-7. [PMID: 22000954 DOI: 10.1016/j.seizure.2011.09.009] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2011] [Revised: 09/25/2011] [Accepted: 09/26/2011] [Indexed: 11/20/2022] Open
Abstract
PURPOSE Ring chromosome 20 {r(20)}--manifests as a refractory epilepsy syndrome with complex partial seizures (CPS), nocturnal frontal lobe seizures and non-convulsive status epilepticus (NCSE) in the majority of cases. r20 lacks a specific phenotypic expression or dysmorphic features. Psychomotor development may be normal, making the diagnosis difficult unless there is a high index of suspicion. This description of further cases is intended to improve recognition of this syndrome. METHODS Karyotyping for r20 was done in patients presenting with cryptogenic refractory epilepsy suggestive of r20 from August 2008 to September 2010. We identified three patients with r20 associated with refractory epilepsy. All were investigated with long-term video EEG. Their unique electro clinical features; epilepsy syndrome and outcome are discussed and compared to the available literature. RESULTS Karyotyping revealed ring 20 in 6-40% of lymphocytes. All manifested with seizures beginning at 2-10years of age. All had CPS; two had NCSE and one a seizure disorder resembling Lennox-Gastaut syndrome. The interictal EEG showed epileptiform abnormalities predominantly over the frontotemporal regions. Two patients had NCSE with generalized, frontally dominant theta and spike and wave discharges. None had facial dysmorphism or imaging abnormalities. They remained resistant to antiepileptic drugs. CONCLUSIONS The use of routine karyotyping can easily pick up r(20); this information is especially useful in resource-poor countries. We have evolved an algorithm stating the indications to attempt r(20) karyotyping in a given patient in the light of the results of the present study and the existing literature.
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Giardino D, Vignoli A, Ballarati L, Recalcati MP, Russo S, Camporeale N, Marchi M, Finelli P, Accorsi P, Giordano L, La Briola F, Chiesa V, Canevini MP, Larizza L. Genetic investigations on 8 patients affected by ring 20 chromosome syndrome. BMC MEDICAL GENETICS 2010; 11:146. [PMID: 20939888 PMCID: PMC2967536 DOI: 10.1186/1471-2350-11-146] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/21/2010] [Accepted: 10/12/2010] [Indexed: 12/23/2022]
Abstract
Background Mosaic Chromosome 20 ring [r(20)] is a chromosomal disorder associated with a rare syndrome characterized by a typical seizure phenotype, a particular electroclinical pattern, cognitive impairment, behavioural problems and absence of a consistent pattern of dysmorphology. The pathogenic mechanism underlying seizures disorders in r(20) syndrome is still unknown. We performed a detailed clinical and genetic study on 8 patients with r(20) chromosome, aimed at detecting the genetic mechanism underlying r(20) syndrome. Methods We submitted 8 subjects with a previous diagnosis of ring 20 chromosome mosaicism to a clinical re-evaluation, followed by cytogenetic, FISH, array-CGH and molecular analyses. The genetic study was also extended to their available parents. Results FISH and array-CGH experiments indicate that cryptic deletions on chromosome 20 are not the cause of the r(20) chromosome associated disease. Moreover, no evidence of chromosome 20 uniparental disomy was found. Analysis of FISH signals given by variant in size alphoid tandem repeats probes on the normal chromosome 20 and the r(20) chromosome in the mosaic carriers suggests that the r(20) chromosome is the same chromosome not circularized in the "normal" cell line. Conclusions Higher percentages of r(20) chromosome cells were observed to be related with precocious age at seizure onset and with resistance to antiepileptic drug treatment. Behavioural problems also seem to be associated with higher percentages of r(20) chromosome cells. Our results suggest that an epigenetic mechanism perturbing 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.
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Affiliation(s)
- Daniela Giardino
- Laboratorio di Citogenetica Medica e Genetica Molecolare, IRCCS Istituto Auxologico Italiano Milan, Italy.
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Herrgård E, Mononen T, Mervaala E, Kuusela L, Aikiä M, Stenbäck U, Pääkkönen L, Airaksinen RL, Kälviäinen R. More severe epilepsy and cognitive impairment in the offspring of a mother with mosaicism for the ring 20 chromosome. Epilepsy Res 2006; 73:122-8. [PMID: 17079116 DOI: 10.1016/j.eplepsyres.2006.09.006] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2006] [Revised: 09/24/2006] [Accepted: 09/26/2006] [Indexed: 10/24/2022]
Abstract
PURPOSE Ring chromosome 20 [r(20)] syndrome is a rare chromosomal disorder. Cases tend to be sporadic. We elucidate the characteristics of an inherited r(20) mosaicism by describing the clinical features of three family members: a mother and her two children. RESULTS The mosaicism rate of the mother was 10% and that of the children 40%. The mother experienced her first epileptic seizures at 24 years of age. Epilepsy was diagnosed two years later. After an unstable period lasting 3 years, she has been seizure-free for 13 years on a combination of valproate and lamotrigine. She has normal intelligence with full working capacity. The daughter exhibited her first epileptic seizures at the age of 7 years and she continues to have seizures weekly. The first epileptic seizures in the son were observed at 5 years of age. The son's epilepsy has been drug resistant from the onset, and a vagal nerve stimulator (VNS) has been ineffective. Psychomotor development was normal in both children up to the onset of epilepsy. Learning difficulties increased throughout school age and both children needed special educational programs. Neuropsychological evaluations have shown deterioration of cognitive levels. Both children had behavioural problems during school age but no longer in adolescence. All three subjects are nondysmophic, normocephalic and of normal growth. CONCLUSION In this family the phenotype of r(20) mosaicism seems to be more severe in the successive generation along with a greater level of mosaicism. The aggravated clinical picture in inherited r(20) mosaicism concerned the onset of epilepsy, drug responsiveness, the cognitive level and behavioural features.
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Ville D, Kaminska A, Bahi-Buisson N, Biraben A, Plouin P, Telvi L, Dulac O, Chiron C. Early pattern of epilepsy in the ring chromosome 20 syndrome. Epilepsia 2006; 47:543-9. [PMID: 16529619 DOI: 10.1111/j.1528-1167.2006.00465.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
PURPOSE The characteristics of epilepsy in ring chromosome 20 have been reported in adolescents and adults. The mode of onset most often remains imprecise. To clarify this onset period, we studied the early-onset features in our personal series and in the reported pediatric cases. METHODS Our series comprises one child with an onset of epilepsy in the neonatal period and five others with an onset before age 8 years. The cases in the literature with an epilepsy onset before 8 years also were reviewed. RESULTS Seizures in the neonatal period were described as motor seizures. Our personal patient with a neonatal onset had severe psychomotor delay. In both infancy and early childhood, the EEG showed no interictal frontal localization of the anomalies, and no long-lasting seizure was recorded. Seizures with terror and hallucinations usually appeared from about age 4 years. It is not before the age of 8 years that the usual interictal EEG pattern appeared of rhythmic theta slow-waves activity with spikes predominating in frontal areas described in adolescence and adulthood. The interictal EEG showed 1- to 2-Hz delta slow waves and spike-and-waves predominating in frontal areas, but no physiologic activity. CONCLUSIONS In ring 20 chromosome, specific epilepsy features are lacking in the neonate, but the whole phenotype shows a more severe expression in terms of mental delay. The characteristic frontal EEG pattern and ictal terror do not appear before age 4 to 5 years.
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Affiliation(s)
- Dorothée Ville
- Department of Clinical Neurophysiology, Hôpital Necker Enfants Malades, Paris, France
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Locharernkul C, Ebner A, Promchainant C. Ring chromosome 20 with nonconvulsive status epilepticus: electroclinical correlation of a rare epileptic syndrome. Clin EEG Neurosci 2005; 36:151-60. [PMID: 16128150 DOI: 10.1177/155005940503600305] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The electroclinical features of two Thai women with ring chromosome 20 and nonconvulsive status epilepticus (NCSE) were studied. Both have also had generalized tonic-clonic seizures and complex partial seizures of varying frequencies since adolescence. Their intellectual functions were normal. Twenty-four-hour video/EEG telemetry recorded during the NCSE showed fluctuating consciousness between overt unresponsiveness and normal awareness. The EEG consisted of long-lasting generalized rhythmic 3-5 Hz sharp or slow waves with a few spikes, lasting several days. Despite the continuous discharges, the patients had relatively subtle clinical episodes of seizures, during which they were sometimes responsive to verbal stimuli. Intravenous antiepileptic drugs (AED) had little effect on the rhythmic EEG. No lesion in their MRIs contributed to NCSE. Ring chromosome 20 was found in 20% of female karyotype in both patients [46,XX,r(20) (p13 q13)/46,XX] but were negative in four healthy siblings. Oral AEDs decreased more than 75% of the overt CPS episodes in both patients at 22 and 26 months of follow-up but had no effect on the natural history of electrical NCSE. The patients' daily activities were minimally affected by the ongoing electrical discharges. These are the first two cases reported of ring chromosome 20 with NCSE in Thailand. Our patients present a rather benign and pharmacologically responsive course probably because of the low percentage of r(20) mosaicism. The electroclinical correlations in our cases raise the possibility that the mechanism of continuous rhythmic waves in this syndrome may be unrelated to epilepsy. Assessing the severity of this syndrome using both clinical seizures and EEG is crucial.
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Affiliation(s)
- Chaichon Locharernkul
- Chulalongkorn Comprehensive Epilepsy Program, King Chulalongkorn Memorial Hospital, Bangkok, Thailand.
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15
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Abstract
Ring chromosome 20 [r(20)] syndrome is a rare chromosomal disorder characterized by epilepsy, mild to moderate mental impairment, and malformation. Patients generally show mosaicism in 1-100% of lymphocytes with r(20). We report here a patient with r(20) syndrome who exhibited mild phenotype with the small ratio of mosaicism (13%) with r(20). Although previous small-scale studies concluded that the mosaicism ratio was unrelated to clinical phenotype, our reassessment of all 57 reported cases has revealed that the ratio is significantly associated with age at seizure onset, intelligence quotient, and malformation, but not with the response of epilepsy to drug treatment. Our results provide important clinical information and prediction for r(20) syndrome.
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Affiliation(s)
- T Nishiwaki
- Department of Neurology, Nara Medical University, Nara, Japan.
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Arnedo N, Nogués C, Bosch M, Templado C. Mitotic and meiotic behaviour of a naturally transmitted ring Y chromosome: reproductive risk evaluation. Hum Reprod 2004; 20:462-8. [PMID: 15528264 DOI: 10.1093/humrep/deh598] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND The mitotic and meiotic behaviour of a transmitted ring Y [r(Y)] chromosome from a father to his Klinefelter syndrome (KS) son, and the mechanism of ring formation are analysed herein. To our knowledge, this is the first reported case of natural transmission of an r(Y). METHODS AND RESULTS Amplification of X chromosome polymorphisms by PCR showed that the KS was of paternal origin. G-banding and fluorescence in situ hybridization (FISH) studies revealed a similar percentage of mosaicism in father and son by mitotic loss of r(Y). SRY gene and Y marker amplification by PCR, FISH with subtelomeric probes for Xp/Yp and Xq/Yq, and comparative genomic hybridization (CGH) analyses indicated the intactness of the Y chromosome from SRY to subtelomere Yq. FISH analysis of sperm from the father showed significantly higher frequencies (P<0.005) for diploidy and for 6, 13, 18, 21, 22, XX, XY disomies than those observed in control donors. CONCLUSIONS An r(Y) with low material loss can be naturally transmitted, showing similar mitotic behaviour in the offspring. The presence of an r(Y) chromosome in germinal cells increased the risk of fathering offspring with numerical abnormalities, even for chromosomes not involved in the arrangement.
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Affiliation(s)
- Núria Arnedo
- Departament de Biologia Cel.lular, Fisiologia i Immunologia, Universitat Autònoma de Barcelona, 08193 Bellaterra, Barcelona, Spain
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Speevak MD, Smart C, Unwin L, Bell M, Farrell SA. Molecular characterization of an inherited ring (19) demonstrating ring opening. Am J Med Genet A 2003; 121A:141-5. [PMID: 12910493 DOI: 10.1002/ajmg.a.20184] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Ring chromosomes arise following breakage in both chromosome arms and rejoining of the centric segment at the broken ends or by end-to-end fusion of the telomeres. The phenotype of ring carriers is unpredictable, and developmental abnormalities may occur even when the ring appears to be structurally balanced. This is believed to be due to mitotic instability from abnormal segregation and sister chromatid exchange in somatic cells. Although ring chromosomes usually arise as de novo events, transmittal from mosaic carriers to offspring sometimes occurs. In such cases, offspring with ring mosaicism in combination with a normal cell line remain unexplained. In this report, we used detailed molecular and cytogenetic analyses of a prenatally detected, inherited ring (19) to observe the behavior of the ring chromosome in culture, and to investigate the mechanism of inherited ring chromosome mosaicism.
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Affiliation(s)
- Marsha D Speevak
- Division of Genetics, Department of Laboratory Medicine, The Credit Valley Hospital, Mississauga, Ontario, Canada.
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Singh R, Gardner RJM, Crossland KM, Scheffer IE, Berkovic SF. Chromosomal abnormalities and epilepsy: a review for clinicians and gene hunters. Epilepsia 2002; 43:127-40. [PMID: 11903458 DOI: 10.1046/j.1528-1157.2002.19498.x] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
PURPOSE We analyzed databases on chromosomal anomalies and epilepsy to identify chromosomal regions where abnormalities are associated with clinically recognizable epilepsy syndromes. The expectation was that these regions could then be offered as targets in the search for epilepsy genes. METHODS The cytogenetic program of the Oxford Medical Database, and the PubMed database were used to identify chromosomal aberrations associated with seizures and/or EEG abnormalities. The literature on selected small anomalies thus identified was reviewed from a clinical and electroencephalographic viewpoint, to classify the seizures and syndromes according to the current International League Against Epilepsy (ILAE) classification. RESULTS There were 400 different chromosomal imbalances described with seizures or EEG abnormalities. Eight chromosomal disorders had a high association with epilepsy. These comprised: the Wolf-Hirschhorn (4p-) syndrome, Miller-Dieker syndrome (del 17p13.3), Angelman syndrome (del 15q11-q13), the inversion duplication 15 syndrome, terminal deletions of chromosome 1q and 1p, and ring chromosomes 14 and 20. Many other segments had a weaker association with seizures. The poor quality of description of the epileptology in many reports thwarted an attempt to make precise karyotype-phenotype correlations. CONCLUSIONS We identified certain chromosomal regions where aberrations had an evident association with seizures, and these regions may be useful targets for gene hunters. New correlations with specific epilepsy syndromes were not revealed. Clinicians should continue to search for small chromosomal abnormalities associated with specific epilepsy syndromes that could provide important clues for finding epilepsy genes, and the epileptology should be rigorously characterized.
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Affiliation(s)
- Rita Singh
- Department of Medicine (Neurology), The University of Melbourne, Austin and Repatriation Medical Centre, Australia
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19
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García DM, Ortiz R, Gómez A, Barriuso E. Ring 20 chromosome syndrome with epilepsy and dysmorphic features: a case report. Epilepsia 2001; 42:1607-10. [PMID: 11879375 DOI: 10.1046/j.1528-1157.2001.29700.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Relatively few cases of the 20 ring chromosome [r(20)] syndrome have been reported. Epileptic seizures, behavioral problems, mental retardation, and absence of definite dysmorphic features characterize this syndrome. We present a patient with the classic genetic and phenotypic findings. A 42-month-old boy with mild dysmorphic features and psychomotor retardation has had generalized tonic-clonic seizures, resistant to antiepileptic drug therapy since he was 26 months old. Electroencephalography (EEG) was performed on several occasions, as were brainstem auditory evoked potentials (BAEPs), magnetic resonance imaging (MRI), and cytogenetic studies. The EEG showed slow waves in anterior regions intermingled with spikes in temporal areas. The BAEPs were abnormal, and neuroimaging studies were normal. The chromosome r(20) appeared in 100 metaphases studied. Parental chromosomes were of normal karyotype. The genetic and EEG finding from this patient strongly suggest that epilepsy associated with 20 ring chromosome syndrome is a distinct new entity, although the clinical manifestations may be broader than previously recognized.
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Affiliation(s)
- D M García
- Servicio de Neurofisiología Clínica, Hospital "Del Río Hortega," Valladolid, Spain
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20
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García-Cruz D, Vásquez AI, Perez-Rulfo D, Dávalos NO, Peñaloza J, García-Ortiz JE, Patiño-García B, Sánchez-Corona J. Ring-20-syndrome and loss of telomeric regions. ANNALES DE GENETIQUE 2000; 43:113-6. [PMID: 11164191 DOI: 10.1016/s0003-3995(00)01027-3] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
A patient aged 10 years and 8 months with a ring-20-syndrome was studied. Clinically he presented normal psychomotor development until 25 months of age when he began with right simple partial motor seizures. He presented minimal dysmorphism, generalized tonic-clonic seizures refractory to medical therapy and behavioral troubles. He was submitted to a callosotomy when he presented an electric status, subsequently, he was treated with anticonvulsivants and felbamate and the seizures were controlled. The karyotype showed a chromosomal complement 46,XY,r(20)(p13q13.3) with loss of the telomeric regions evidenced by FISH. The mother had normal karyotype. The clinical and cytogenetic features of previous cases described in the literature were compared leading to a better characterization of this syndrome.
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Affiliation(s)
- D García-Cruz
- Division de Genética, Centro de Investigación Biomédica de Occidente, CMNO, IMSS, Guadalajara, Jalisco, Mexico.
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21
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Kobayashi K, Inagaki M, Sasaki M, Sugai K, Ohta S, Hashimoto T. Characteristic EEG findings in ring 20 syndrome as a diagnostic clue. ELECTROENCEPHALOGRAPHY AND CLINICAL NEUROPHYSIOLOGY 1998; 107:258-62. [PMID: 9872443 DOI: 10.1016/s0013-4694(98)00069-8] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
OBJECTIVE To review the EEG features of ring 20 syndrome in two patients and determine the characteristic pattern of this syndrome. The features of our cases and 24 patients reported in the literature will be discussed. SUBJECTS AND METHODS Report of two patients and review of literature. RESULTS The two patients had intractable epilepsy since childhood. Their clinical seizures were mostly complex partial seizures. Often the patients seizures were of prolonged duration. Ictal EEG revealed characteristic slow waves, and sharp waves. The slow waves were (1) usually synchronous high-voltage slow waves with or without a spike component predominantly in the frontal and frontopolar areas, (2) sometimes showed a change in frequency every several seconds, (3) continued for a long period, and (4) easily spread diffusely. The sharp waves were 5-6 Hz irregular and diffuse discontinuous sharp waves, and sometimes appeared predominantly in the centroparietal area. The clinical seizure pattern and EEG findings were similar in the 24 published cases. CONCLUSIONS These EEG findings may be a characteristic feature of ring 20 syndrome and thus may be useful as a diagnostic clue.
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Affiliation(s)
- K Kobayashi
- Department of Child Neurology, National Center Hospital for Mental, Nervous and Muscular Disorders, NCNP, Tokyo, Japan
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22
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Canevini MP, Sgro V, Zuffardi O, Canger R, Carrozzo R, Rossi E, Ledbetter D, Minicucci F, Vignoli A, Piazzini A, Guidolin L, Saltarelli A, dalla Bernardina B. Chromosome 20 ring: a chromosomal disorder associated with a particular electroclinical pattern. Epilepsia 1998; 39:942-51. [PMID: 9738673 DOI: 10.1111/j.1528-1157.1998.tb01443.x] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
PURPOSE The chromosome 20 ring [r(20)] is a rare chromosomal disorder without clear phenotypical markers. We describe the electroclinical pattern in a group of patients with r(20). METHODS We observed 3 patients (a boy, patient 1; his mother, patient 2; and an unrelated man, patient 3), performing prolonged video-EEG and cytogenetic studies and fluorescent in situ hybridization (FISH) with chromosome-specific telomeric probes. RESULTS All 3 patients had a very similar abnormal electroclinical pattern characterized by long bursts or trains of rhythmic theta waves, which were sharply contoured or had a notched appearance (with no detectable clinical correlate), and generalized spike waves (SW) associated with seizures of probable frontotemporal origin (SFT). In all 3 patients, the cytogenetic analysis of T lymphocytes showed mosaicism with a normal cell line and a second cell line with a chromosome 20, although the latter was little represented in patients 2 and 3. A few cells with a single chromosome 20 were also found. The same cytogenetic findings were confirmed in the lymphoblastoid cell line of patient 1 and in the fibroblasts of patient 3. FISH with chromosome-specific telomeric probes and TTAGGG sequences demonstrated the integrity of the ring chromosomes. CONCLUSIONS The clinical picture of these patients appears to be related to the instability of the r(20)-generating cells monosomic for chromosome 20 and is thus haploinsufficient for a gene. In these patients, the electroclinical pattern of theta waves (probably unrelated to epilepsy) and the SW and SFT, even with mild mental retardation (MR) or no MR and without dysmorphic features, suggest that the r(20) syndrome may be present.
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Affiliation(s)
- M P Canevini
- Centro Regionale Epilessia, Ospedale San Paolo, Università degli Studi, Milan, Italy
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23
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Abstract
We reported a 24-year-old woman with moderate mental retardation and partial epilepsy. She developed complex partial seizures at 3 years of age and generalized tonic convulsions at 9 years. Chromosome analysis revealed that she had mosaicism (87%) of 46, XX, and r(20) (p13,q13.3). Her electroencephalogram showed bilateral 2-3 Hz sharp and wave complex over the bilateral frontopolar, and centro-parieto-occipital areas. Computed tomographic and magnetic resonance image examinations were normal. Twenty-five cases of ring 20 chromosome karyotypes (including this case) have been reported in the literature; 19 showed epilepsy, and 18 showed moderate mental retardation. Many of the patients showed growth retardation and minor malformations. The ring 20 syndrome is associated with a high incidence of epilepsy, particularly partial epilepsy. Our findings indicate that the main features of the ring 20 syndrome are partial epilepsy and mental retardation.
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Affiliation(s)
- H Yamadera
- Department of Neuropsychiatry, Nippon Medical School, Tokyo, Japan
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24
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Flejter WL, Finlinson D, Root S, Nguyen W, Brothman AR, Viskochil D. Familial ring (19) chromosome mosaicism: case report and review. AMERICAN JOURNAL OF MEDICAL GENETICS 1996; 66:276-80. [PMID: 8985487 DOI: 10.1002/(sici)1096-8628(19961218)66:3<276::aid-ajmg8>3.0.co;2-n] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Ring (19) chromosomal mosaicism has been identified in a 14-month-old girl referred for cytogenetic evaluation due to microcephaly and developmental delay with autistic-like mannerisms. An analysis of her peripheral blood lymphocytes showed a 46,XX,r(19) cell line in 119/121 of cells examined. Of the two remaining cells, one had a normal female chromosome complement and the other showed loss of one of the chromosome 19 homologs. Further analysis by fluorescence in situ hybridization using an all human telomere probe showed the presence of a single hybridization signal on the r(19) chromosome. Subsequent cytogenetic characterization of cells derived from the patient's phenotypically normal mother also demonstrated the presence of a ring 19 chromosome in 4/100 cells. The remaining cells had a normal female chromosome complement. These findings represent the first reported case of familial ring 19 mosaicism. The cytogenetic and clinical findings in these two individuals are discussed in relation to six previously reported cases of de novo ring chromosome 19 mosaicism.
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Affiliation(s)
- W L Flejter
- Departments of Pediatrics, University of Utah 84132, USA
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25
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Takahashi Y, Shigematsu H, Kubota H, Inoue Y, Fujiwara T, Yagi K, Seino M. Nonphotosensitive video game-induced partial seizures. Epilepsia 1995; 36:837-41. [PMID: 7635104 DOI: 10.1111/j.1528-1157.1995.tb01623.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
We report a 9-year-old boy with a ring 20 chromosome anomaly whose complex partial seizures (CPS), presumably of frontal lobe origin, were often induced by playing video games. Neither photosensitivity nor pattern sensitivity was observed. An intensive video-EEG investigation showed that video games as well as mental calculation elicited rhythmic runs of bilateral high-voltage slow waves, which eventually evolved into ictal discharges. This case suggests that higher brain functions can be involved in seizure induction.
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Affiliation(s)
- Y Takahashi
- National Epilepsy Center, Shizuoka Higashi Hospital, Japan
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26
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Brandt CA, Kierkegaard O, Hindkjaer J, Jensen PK, Pedersen S, Therkelsen AJ. Ring chromosome 20 with loss of telomeric sequences detected by multicolour PRINS. Clin Genet 1993; 44:26-31. [PMID: 8403451 DOI: 10.1111/j.1399-0004.1993.tb03837.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
A ring chromosome 20 in a male infant with epileptic seizures, mental and somatic growth retardation, and behavioural disturbances is described. Conventional cytogenetics revealed the karyotype to be 46,XY,r(20)(pter-->qter) and no signs of mosaicism were found. Fluorescence in situ hybridisation using the clone p20Z1 identified the ring to be derived from chromosome 20. By counting 111 metaphases, only 7% were found to be missing the ring. The absence of telomeric sequences in the ring chromosome was demonstrated by multicolour PRINS: a three-step PRimed IN Situ labelling technique, using unlabelled primers. A terminal deletion of both arms thus seems to be the cause of the ring formation in the proband. Bivariate flow-analysis of chromosomes verified a deletion of the ring chromosome. The clinical and cytogenetic findings are compared with previous cases. A specific ring 20 syndrome seems justified.
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Affiliation(s)
- C A Brandt
- Institute of Human Genetics, University of Aarhus, Denmark
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27
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Lancman ME, Penry JK, Asconape JJ, Brotherton TA. Number 20 ring chromosome: a case with complete seizure control. J Child Neurol 1993; 8:186-7. [PMID: 8505482 DOI: 10.1177/088307389300800214] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
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