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Bouhamdani N, McConkey H, Leblanc A, Sadikovic B, Amor MB. Diagnostic utility of DNA methylation episignature analysis for early diagnosis of KMT2B-related disorders: case report. Front Genet 2024; 15:1346044. [PMID: 38425714 PMCID: PMC10902455 DOI: 10.3389/fgene.2024.1346044] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2023] [Accepted: 01/29/2024] [Indexed: 03/02/2024] Open
Abstract
The lysine methyltransferase 2B (KMT2B) gene product is important for epigenetic modifications associated with active gene transcription in normal development and in maintaining proper neural function. Pathogenic variants in KMT2B have been associated with childhood-onset Dystonia-28 and Intellectual developmental disorder, autosomal dominant 68 (MRD 68) for cases of neurodevelopmental impairment without dystonia (DYT28; OMIM 617284 and MRD68; OMIM 619934, respectively). Since its first description in 2016, approximately one hundred KMT2B genetic variants have been reported with heterogeneous phenotypes, including atypical patterns of dystonia evolution and non-dystonic neurodevelopmental phenotypes. KMT2B-related disorders share many overlapping phenotypic characteristics with other neurodevelopmental disorders and delayed dystonia, that can appear later in childhood, often delaying clinical diagnosis. Furthermore, conventional genetic testing may not always provide actionable information (e.g., gene panel selection based on early clinical presentation or variants of uncertain significance), which prevents patients and families from obtaining early access to treatments and support. Herein, we describe the early diagnosis of KMT2B-related neurodevelopmental disorder by DNA methylation episignature testing in a 4-year-old patient without features of dystonia at diagnosis, which is reported to develop in more than 80% of KMT2B-related disorder cases. The proband, a 4-year-old female of Jewish-Israeli descent, presented with speech delay, microcephaly, poor weight gain, attention-deficit and hyperactivity disorder, dysmorphism, intellectual disabilities and joint hyperlaxity, but presented no signs of dystonia at initial evaluation. Episignature screening in this pre-symptomatic patient enabled accurate genetic diagnosis and timely and actionable intervention earlier in the natural history of Childhood-onset Dystonia-28.
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Affiliation(s)
- Nadia Bouhamdani
- Vitalité Health Network, Moncton, NB, Canada
- Faculty of medicine and health sciences, Université de Sherbrooke, Sherbrooke, QC, Canada
- Centre de Formation Médicale du Nouveau-Brunswick, Université de Moncton, Moncton, NB, Canada
- Department of Chemistry and Biochemistry, Université de Moncton, Moncton, NB, Canada
| | - Haley McConkey
- Verspeeten Clinical Genome Centre, London Health Sciences Centre, London, ON, Canada
- Department of Pathology and Laboratory Medicine, Schulich School of Medicine and Dentistry Western University, London, ON, Canada
| | - Amélie Leblanc
- Vitalité Health Network, Moncton, NB, Canada
- Faculty of medicine and health sciences, Université de Sherbrooke, Sherbrooke, QC, Canada
- Centre de Formation Médicale du Nouveau-Brunswick, Université de Moncton, Moncton, NB, Canada
| | - Bekim Sadikovic
- Verspeeten Clinical Genome Centre, London Health Sciences Centre, London, ON, Canada
- Department of Pathology and Laboratory Medicine, Schulich School of Medicine and Dentistry Western University, London, ON, Canada
| | - Mouna Ben Amor
- Vitalité Health Network, Moncton, NB, Canada
- Faculty of medicine and health sciences, Université de Sherbrooke, Sherbrooke, QC, Canada
- Centre de Formation Médicale du Nouveau-Brunswick, Université de Moncton, Moncton, NB, Canada
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Erro R, Monfrini E, Di Fonzo A. Early-onset inherited dystonias versus late-onset idiopathic dystonias: Same or different biological mechanisms? INTERNATIONAL REVIEW OF NEUROBIOLOGY 2023; 169:329-346. [PMID: 37482397 DOI: 10.1016/bs.irn.2023.05.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/25/2023]
Abstract
Dystonia syndromes encompass a heterogeneous group of movement disorders which might be differentiated by several clinical-historical features. Among the latter, age-at-onset is probably the most important in predicting the likelihood both for the symptoms to spread from focal to generalized and for a genetic cause to be found. Accordingly, dystonia syndromes are generally stratified into early-onset and late-onset forms, the former having a greater likelihood of being monogenic disorders and the latter to be possibly multifactorial diseases, despite being currently labeled as idiopathic. Nonetheless, there are several similarities between these two groups of dystonia, including shared pathophysiological and biological mechanisms. Moreover, there is also initial evidence of age-related modifiers of early-onset dystonia syndromes and of critical periods of vulnerability of the sensorimotor network, during which a combination of genetic and non-genetic insults is more likely to produce symptoms. Based on these lines of evidence, we reappraise the double-hit hypothesis of dystonia, which would accommodate both similarities and differences between early-onset and late-onset dystonia in a single framework.
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Affiliation(s)
- Roberto Erro
- Department of Medicine, Surgery and Dentistry "Scuola Medica Salernitana", University of Salerno, Baronissi, SA, Italy.
| | - Edoardo Monfrini
- Foundation IRCCS Ca' Granda Ospedale Maggiore Policlinico, Neurology Unit, Milan, Italy; Dino Ferrari Center, Neuroscience Section, Department of Pathophysiology and Transplantation, University of Milan, Milan, Italy
| | - Alessio Di Fonzo
- Foundation IRCCS Ca' Granda Ospedale Maggiore Policlinico, Neurology Unit, Milan, Italy
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