Epilepsy-dyskinesia syndromes (EDS) are a complex group of neurogenetic disorders characterized by the co-occurrence of epilepsy and movement disorders. Despite their increasing clinical recognition, the molecular and clinical spectrum of EDS remains poorly understood. While numerous genetic aetiologies have been implicated, systematic characterization across diverse populations is lacking. This study aimed to delineate the molecular and clinical landscape of EDS in a large, multinational cohort, focusing on movement disorder phenomenologies, genotype-phenotype correlations, and treatment responses. We conducted a multicentre, cross-sectional study involving 609 patients with childhood-onset movement disorders associated with pathogenic variants in 105 predefined genes. Clinical data were collected from over 30 centres across 25 countries using a standardized survey, capturing movement disorder phenomenologies, seizure types, developmental trajectories, motor function and treatment outcomes. We classified EDS-associated genes into biologically meaningful groups by performing unsupervised clustering, which integrated protein-protein interactions and functional data. Genotype-phenotype correlations were assessed using a one-versus-remainder approach to quantify differential enrichment of clinical manifestations and treatment responses. Pathogenic variants were identified in 74 of the 105 predefined genes, with 12 genes accounting for two-thirds of cases. The most frequently reported genes were MECP2, ATP1A3, and GNAO1. Data-driven gene cluster analysis identified 12 functional groups, mapping EDS to relevant biological pathways and informing genotype-phenotype analyses. Dystonia (34.2%), stereotypies (24.6%) and ataxia (16.2%) were the most prevalent movement disorders, with gene- and pathway-specific movement disorder signatures extending beyond previously known associations. Notably, most patients exhibited mixed movement disorders, highlighting the phenotypic complexity of EDS. Epilepsy was diagnosed in only 66.8% of cases, suggesting that some EDS primarily manifest as movement disorders. Developmental trajectories varied by genetic aetiology. Pharmacological responses demonstrated gene- and pathway-specific treatment effects, confirming established therapeutic associations (e.g. PRRT2 variants responding to carbamazepine) and identifying previously unrecognized effects, such as exacerbation of motor symptoms with levodopa/carbidopa in GNAO1 and MECP2 variants. This study provides a detailed characterization of EDS, identifying distinct genetic, phenotypic and therapeutic patterns. The findings underscore the need for early recognition of movement disorders within epilepsy cohorts, offer immediate insights to improve anticipatory guidance and clinical management of EDS, and advocate for personalized treatment strategies. By laying the groundwork for longitudinal studies to refine genotype-phenotype correlations and establish a natural history, this work paves the way for interventional clinical trials and precision medicine approaches.

BACKGROUND:NKX2-1-related disorders result from heterozygous variants in NKX2-1, a gene crucial for brain, lung, and thyroid development. Although movement disorders, hypothyroidism, and neonatal respiratory distress are recognized, the full phenotype and genotype-phenotype relationships remain incompletely defined. OBJECTIVES:To delineate neurological, respiratory, and endocrine features across ages, characterize movement disorder trajectories - particularly chorea - and explore genotype-phenotype associations with clinical relevance. METHODS:We conducted a multicenter, cross-sectional study recruiting participants through referral clinicians and European networks. Standardized clinical and genetic data were captured in an electronic database and analyzed with descriptive and inferential statistics. RESULTS:Sixty-eight individuals (37 female; median age 16 years, range 2-60 years) were included. Motor delay was the commonest presenting feature (~60%); neonatal respiratory distress syndrome occurred in one-third of cases. The brain-lung-thyroid triad was present in almost half. Chorea affected over 90% and began in early childhood; it was more frequent with single nucleotide variants than with deletions. Deletions are associated with better gross motor function. Frameshift or nonsense variants showed greater respiratory involvement, and variants in the exon-3 homeobox region were associated with age-related reduction of chorea. Neonatal respiratory distress predicted later respiratory symptoms. Greater abnormal involuntary movement severity correlated with poorer manual and gross motor function. Hypotonia and untreated hypothyroidism are associated with more severe chorea. Psychiatric comorbidity occurred in over one-third of cases, mainly attention-deficit/hyperactivity symptoms. CONCLUSIONS:This largest cohort to date shows early neurological onset, genotype-specific outcomes, and frequent psychiatric comorbidity in NKX2-1-related disorders, refining clinical expectations and supporting genotype-informed diagnosis, counseling, and management. © 2026 The Author(s). Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

BACKGROUND/OBJECTIVES:To study the hypothesis that cognitive functions and learning skills are impaired in child/adolescent childhood cancer survivors (CCS). Secondary outcomes included psychosocial parameters and quality of life. METHODS:This case-control study was conducted over four years (2017-2021) at the largest pediatric Aghia Sophia Children's Hospital, in Greece. Eligible participants were children and adolescents in Greece. For CCS, ≥1 year should have elapsed from completion of cancer treatment. Assessments of neurocognitive function, learning and psychosocial skills and health-related quality of life (HRQoL) were performed with validated instruments (WISC-III, LAMDA software, Achenbach CBCL/6-18 and YSR, KIDSCREEN-52, respectively). RESULTS:In total, 219 participants (47.49% males, mean age ± SD 11.72 ± 2.32 years), 70 CCS and 149 controls (matched for age, sex, family income), were included. Cases were CCS of acute lymphoblastic leukemia (n = 25)/brain tumors (n = 19)/lymphoma (n = 17)/nephroblastoma (n = 5)/Ewing sarcoma (n = 3)/rhabdomyosarcoma (n = 1). CCS had worse scores in full-scale Intelligence Quotient (FSIQ) (p = 0.004), verbal IQ (VIQ) (p = 0.005) and all its subscales, performance IQ (PIQ) (p = 0.021), and almost all learning parameters than controls. Attention, working memory, writing/visual-motor coordination, processing accuracy/speed, language acquisition/expression, all psychosocial scales, and HRQoL domains of mood and emotions, were negatively affected in CCS. Female CCS demonstrated lower FSIQ (p = 0.019) and VIQ (p = 0.014) than control females, whereas male CCS retained their total IQ unaffected. Among CCS, those with non-central nervous system (CNS) tumors, higher parental educational level or higher family income had significantly higher IQ than those with CNS tumors, lower parental educational level or lower family income, respectively. CONCLUSIONS:CCS in Greece carry a significant burden of cognitive and psychological morbidity. Cognitive/educational and psychosocial support to CCS is imperative.

Background/Objectives: Genomic sequencing can shorten the diagnostic pathway for selected symptomatic neonates and young infants, but evidence from such cohorts should not be extrapolated to population newborn screening. This study describes molecular findings and potential clinical implications in 25 unrelated patients younger than 6 months at referral with heterogeneous, predominantly neurological phenotypes and no established molecular diagnosis. Methods: The first 17 patients underwent whole-exome sequencing (WES), and the subsequent 8 underwent whole-genome sequencing (WGS) under sequential laboratory protocols; allocation was not randomized, and the study was not designed to compare platforms. Results: Pathogenic or likely pathogenic findings providing a definitive or likely molecular diagnosis were identified in 7/25 patients (28.0%; 95% confidence interval [CI], 14.3-47.6), including sequence variants, one 20q13.33 deletion, and mosaic trisomy 9. An additional RANBP2 variant was interpreted as a susceptibility-associated finding in a patient with infection-related encephalitis, yielding clinically relevant findings in 8/25 patients (32.0%; 95% CI, 17.2-51.6). Three definitive diagnoses involved disorders with established disease-specific management considerations; however, patient-level treatment changes, turnaround times, and outcomes were not systematically assessed. Conclusions: These findings support the diagnostic value of genomic testing in selected symptomatic neonates and young infants, while the small, heterogeneous cohort, sequential non-equivalent workflows, and incomplete outcome data preclude conclusions about comparative WES/WGS performance or population newborn screening.

Background:Café-au-lait macules (CALMs) are often the earliest visible sign of neurofibromatosis type 1 (NF1), a genetic disorder with marked clinical variability. Early characterization of CALM patterns may aid in anticipating systemic disease burden. Objective:To analyze the early appearance, anatomical distribution, and number of CALMs in children with genetically confirmed NF1 and explore associations with central nervous system (CNS) and skeletal manifestations. Methods:We retrospectively reviewed children with genetically confirmed NF1 at a tertiary pediatric hospital in Athens, Greece (2018-2023). Demographic data, CALM count and distribution, mutation type, and systemic involvement were recorded. CALMs were documented through standardized dermatologic assessment and clinical photography. Statistical correlations were evaluated using nonparametric tests. Results:Sixty-three children (33 males, 30 females; mean age 7.5 ± 4.6 years) were included. All had more than 6 CALMs (mean 18.1 per child), most frequently on the thoracic region (53.6%). In 38.1% of patients, more than 6 CALMs were present by 6 months; among those with 6 or fewer at 6 months, 94.9% exceeded this threshold by 24 months. Children with 7-12 CALMs at 12 months had significantly higher frequencies of CNS and skeletal manifestations (P < .05). Conclusion:CALMs were predominantly thoracic and showed the steepest increase between 6 and 12 months. Children with 7-12 CALMs at 12 months had greater systemic involvement, supporting early, risk-adapted surveillance strategies in pediatric NF1.

Tyrosine hydroxylase (TH) catalyses the rate-limiting step in dopamine biosynthesis. Autosomal recessive tyrosine hydroxylase deficiency (THD) leads to clinical phenotypes reflecting the deficiency of dopamine, norepinephrine, or epinephrine in the central nervous system (CNS), presenting along a continuous spectrum from mild to severe forms of the disease. The diagnosis is suggested by the detection of low CSF homovanillic acid (HVA) and confirmed by identifying biallelic pathogenic variants in the TH gene. L-dopa/decarboxylase inhibitor (DCI) supplementation is often the first-line treatment, and most patients have a good therapeutic response. However, initiation of therapy can be challenging in patients with severe disease forms who develop L-dopa/DCI-induced dyskinesia. Therefore, alternative treatment options, such as monoamine oxidase (MAO) inhibitors, must be evaluated to optimize motor symptom control. Clinical experience suggests that early diagnosis and treatment initiation may improve the outcome. Additionally, a multidisciplinary treatment approach should be utilized to monitor neurocognitive development and other comorbidities that may occur in THD. In this consensus guideline, representatives of the International Working Group on Neurotransmitter related Disorders (iNTD) and patient advocates evaluated all the evidence available in the literature on the diagnosis and management of THD and developed recommendations using the SIGN and GRADE methodologies. Based on the limited evidence, practical recommendations have been developed to support clinical diagnosis, laboratory testing, neuroimaging, medical treatment, and non-medical interventions. Research topics for further development were identified. This guideline aims to improve the care of patients with THD worldwide and raise general awareness of this rare disease.

BACKGROUND:Parkinsonism in infancy is rare and is highly correlated with the presence of dystonia. Advances in treating and characterizing developmental and infantile degenerative parkinsonism have highlighted the need for a specialized assessment scale. OBJECTIVE:The aim of this study was to design and validate a scale that effectively assesses parkinsonism-dystonia in early life. METHODS:The Infantile Parkinsonism-Dystonia Rating Scale (IPDRS) was designed to capture the key clinical features of parkinsonism-dystonia in early life. It consists of 28 items across three subscales: Non-motor symptoms, Motor symptoms, and Dyskinesias. Thirty-two patients with hypokinetic movement disorder were scored following a standardized protocol. Filmed motor examinations were analyzed independently by three pediatric movement disorders specialists to evaluate interrater reliability. Twenty additional patients with primary neurotransmitter disorders were scored, and nine of them were evaluated at baseline and after treatment. Psychometric validation was conducted. RESULTS:A total of 52 patients were scored using the IPDRS. Mean age was 3.1 years (standard deviation [SD]: 2.0), and the mean IPDRS score was 40.8 (SD: 13.17). Internal consistency analysis demonstrated a Cronbach's α of 0.21 for Non-motor symptoms subscale, 0.84 for Motor symptoms subscale, and 0.95 for Dyskinesia subscale. Kappa indexes exceeded 0.70 in seven items. Correlation coefficients for dystonia items with the Barry-Albright-Dystonia Scale ranged from 0.46 to 0.64. After treatment, all IPDRS scores changed significantly, with an effect size of 2.42. CONCLUSIONS:The IPDRS appears to be a reliable and valid tool for assessing parkinsonism in early life. Further validation studies with a larger sample size are needed to confirm these findings and complete the validation process. © 2025 The Author(s). Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

BACKGROUND:Dystonia in childhood is typically associated with cerebral palsy (CP). Dystonia severity scales for CP require prolonged exam protocols with numerous tasks, often making them onerous for routine clinical use. We aimed to identify which individual tasks best approximate dystonia severity compared to the gold standard full protocol. METHODS:In this cross-sectional study, comprehensive exam protocol videos were taken during routine care of ambulatory people with CP age 5 years and up. Five pediatric dystonia experts reviewed individual tasks and the full protocol for dystonia using the Global Dystonia Severity Rating Scale. Experts' written scoring justifications were qualitatively analyzed to determine commonly cited features of dystonia. RESULTS:When examining the difference in dystonia severity ratings between each task and the full protocol, seated upper extremity tasks had the lowest variance (P < 0.05, F-test) and had lower score differences than the stand/walk/run and seated lower extremity tasks (P < 0.05, repeated measures Friedman test). Experts most commonly identified the following movements as dystonic: wrist flexion (8.4% of all movement statements), finger flexion (7.3%), wrist ulnar deviation (6.8%), toe dorsiflexion (8.4%), ankle inversion (7.9%), and ankle plantarflexion (6.4%). Experts rated dystonic movements as more severe if they were consistently triggered by multiple stimuli (26.8% of all severity statements) or functionally impactful (20.7%). CONCLUSIONS:Seated upper extremity tasks may be valuable for identifying dystonia and estimating its severity during routine clinical care. Clinical dystonia severity assessment could be guided by assessing specific dystonic movements, the consistency with which they are triggered, and their functional impact.

Background: Kleefstra syndrome 1(KLEFS1, OMIM#610253) is a rare neurodevelopmental disorder (NDD) instigated by heterozygous variants or microdeletions occurring in the 9q34.4 genomic region of the euchromatic histone methyltransferase-1 (EHMT1) gene and is inherited in an autosomal dominant (AD) manner. The clinical phenotype of KLEFS1 includes moderate to severe intellectual disability (ID), hypotonia, and distinctive facial features and additionally involves other organ systems (heart, renal, genitourinary, sensory) albeit with phenotypic heterogeneity between patients. The purpose of this study is to expand the genotypic spectrum of KLEFS1 and compare phenotypic features of the syndrome of already published cases. Methods: Exome sequencing (ES), chromosomal microarray analysis (CMA), as well as sanger sequencing, for confirmation of the de novo status of the frameshift variant, were used. Results: Here we describe two more cases, both males with a similar age and carriers of novel variants; one with a frameshift variant involving exon 13: p.Val692Glyfs*64 and the other with the smallest so far described, 11 Kb (exons 19-25), 9q34.4 microdeletion: 9q34.3 (140703393-140714454). Both presented with an NDD disorder with one showing more severe ID with significant social disabilities, while the other with the microdeletion had mild ID and following a normal education curriculum. Neither of them were obese nor had any other significant organ system disorder. Conclusions: The observed phenotypic variability due to genotypic differences in the two children contributes to the expanding spectrum of KLEFS1 disease phenotypes.

BACKGROUND:Tuberous Sclerosis Complex (TSC) is a rare, multisystem genetic disorder with highly variable clinical manifestations. While international registries such as TOSCA have provided large-scale data, national-level studies remain limited. This study represents the first national cohort analysis of TSC patients in Greece, providing comprehensive insights into clinical characteristics, genotype-phenotype correlations, and previously underreported rare manifestations. METHODS:A descriptive analysis was conducted on 115 TSC patients diagnosed based on the latest criteria. Clinical, genetic, and treatment-related data were analysed, with a particular focus on neurological, renal, cardiac, dermatological, and pulmonary manifestations, as well as rare or atypical disease presentations. RESULTS:The median age at diagnosis was 1.2 years (range: 0-43 years). Epilepsy was the most frequent initial symptom (70.4 %), with drug-resistant epilepsy (DRE) affecting 39.5 % of cases. Intellectual disability, autism spectrum disorder, and behavioral issues correlated significantly with early seizure onset and TSC2 variants. Common manifestations include cortical tubers (93.9 %), subependymal nodules (92.2 %), angiomyolipomas (48.7 %), and cardiac rhabdomyoma (33 %). Notably, we report several rare manifestations, including high-grade glioma in a pediatric patient, diffuse lipomatosis, pancreatic neuroendocrine tumours, rectal polyps, and erythema nodosum presented in a patient on everolimus therapy, further highlighting the systemic complexity and malignancy risks in TSC. CONCLUSIONS:Our study provides novel epidemiological and clinical data on TSC in Greece, reinforcing genotype-phenotype correlations and expanding the spectrum of rare manifestations. These findings emphasise the need for lifelong surveillance, multidisciplinary management, and early detection strategies to mitigate long-term complications. This study also contributes to the broader understanding of TSC by documenting atypical presentations that may inform future clinical guidelines and patient care strategies.

BACKGROUND:Patients with mutations in the monocarboxylate transporter 8 (MCT8, SLC16A2) suffer from X-linked recessive Allan-Herndon-Dudley syndrome (AHDS), which is characterized by developmental delay and a severe movement disorder. Current trials using thyroid hormone derivatives to overcome the transporter defect have failed to achieve patient-oriented therapeutic goals. OBJECTIVES:Our aim was to define the type of movement disorder in AHDS in an observational cohort study and to investigate the causative role of the dopaminergic system. METHODS:We present longitudinal clinical data from the DEEPTYPE registry of 11 patients with video documentation, standardized phenotyping, cerebrospinal fluid (CSF) analysis, neuroimaging data, and the treatment response to levodopa/carbidopa supplementation. RESULTS:Children presented with signs of childhood parkinsonism, including hypokinesia, hypomimia, inability to sit or stand, rigidity, dystonia, and autonomic dysfunction. CSF homovanillic acid concentrations were decreased (n = 12), suggesting an isolated dopamine pathway impairment. Seven out of 8 patients responded favorably to l-dopa/carbidopa supplementation and we did not observe any adverse drug reactions. CONCLUSIONS:AHDS is associated with childhood parkinsonism, which is linked with biochemical abnormalities of dopamine metabolism. It can be treated with l-dopa/carbidopa supplementation. However, further research is needed to elucidate the exact effect of MCT8 deficiency on dopamine metabolism. © 2025 The Author(s). Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

INTRODUCTION/AIMS:Myotonia congenita (MC) is the most common hereditary channelopathy in humans. Characterized by muscle stiffness, MC may be transmitted as either an autosomal dominant (Thomsen) or a recessive (Becker) disorder. MC is caused by variants in the voltage-gated chloride channel 1 (CLCN1) gene, important for the normal repolarization of the muscle action potential. More than 250 disease-causing variants in the CLCN1 gene have been reported. This study provides an MC genotype-phenotype spectrum in a large cohort of Greek patients and focuses on novel variants and disease epidemiology, including additional insights for the variant CLCN1:c.501C > G. METHODS:Sanger sequencing for the entire coding region of the CLCN1 gene was performed. Targeted segregation analysis of likely candidate variants in additional family members was performed. Variant classification was based on American College of Medical Genetics (ACMG) guidelines. RESULTS:Sixty-one patients from 47 unrelated families were identified, consisting of 51 probands with Becker MC (84%) and 10 with Thomsen MC (16%). Among the different variants detected, 11 were novel and 16 were previously reported. The three most prevalent variants were c.501C > G, c.2680C > T, and c.1649C > G. Additionally, c.501C > G was detected in seven Becker cases in-cis with the c.1649C > G. DISCUSSION:The large number of patients in whom a diagnosis was established allowed the characterization of genotype-phenotype correlations with respect to both previously reported and novel findings. For the c.501C > G (p.Phe167Leu) variant a likely nonpathogenic property is suggested, as it only seems to act as an aggravating modifying factor in cases in which a pathogenic variant triggers phenotypic expression.

Newborn screening using biochemical tests is a widespread practice. However, the recent availability of genetic sequencing has enabled the rapid screening of many monogenic disorders. The purpose of our study was to assess the outcomes of whole exome sequencing (WES) and whole genome sequencing (WGS) as the primary newborn screening test. This cohort study enrolled 26 symptomatic neonates and infants exhibiting a spectrum of neurological symptoms and issues. Genome sequencing (GS) identified relevant diagnostic variants in 9 patients (point mutations, CNVs and one case of aneuploidy), suggesting that using GS as the primary newborn screening test in a general newborn population enhances traditional screening's detection capabilities. This evidence-based finding may support considering GS as a critical method for first-tier screening.

Spastic cerebral palsy (CP) is the most common type of CP. Its natural history has been well-documented, and guidelines for managing spasticity have long been available. Dyskinetic CP accounts for up to 15% of cases of CP, motor impairments are often more severe and refractory to treatment, and its natural history has not been well delineated. Despite the recent development of guidelines for the management of dyskinetic CP, the unique needs of patients with this type of CP remain largely uncharacterized and unaddressed ( 1 Colver A. Fairhurst C. Pharoah P.O. Cerebral palsy. Lancet. 2014 Apr 5; 383 (Epub 2013. PMID: 24268104): 1240-1249https://doi.org/10.1016/S0140-6736(13)61835-8 Abstract Full Text Full Text PDF PubMed Scopus (415) Google Scholar , 2 Gilbert L.A. Fehlings D.L. Gross P. Kruer M.C. Kwan W. Mink J.W. Shusterman M. Aravamuthan B.R. Cerebral Palsy Research Network Dystonia Study GroupTop 10 Research Themes for Dystonia in Cerebral Palsy: A Community-Driven Research Agenda. Neurology. 2022; 99 (Epub 2022. PMID: 35715199; PMCID: PMC9442618): 237-245https://doi.org/10.1212/WNL.0000000000200911 Crossref PubMed Scopus (9) Google Scholar , 3 Fehlings D. Agnew B. Gimeno H. Harvey A. Himmelmann K. Lin J.P. Mink J.W. Monbaliu E. Rice J. Bohn E. Falck-Ytter Y. Pharmacological and neurosurgical management of cerebral palsy and dystonia: Clinical practice guideline update. Dev Med Child Neurol. 2024; (Epub ahead of print. PMID: 38640091)https://doi.org/10.1111/dmcn.15921 Crossref PubMed Scopus (1) Google Scholar ).

SCN1A, the gene encoding for the Nav1.1 channel, exhibits dominant interneuron-specific expression, whereby variants disrupting the channel’s function affect the initiation and propagation of action potentials and neuronal excitability causing various types of epilepsy. Dravet syndrome (DS), the first described clinical presentation of SCN1A channelopathy, is characterized by severe myoclonic epilepsy in infancy (SMEI). Variants’ characteristics and other genetic or epigenetic factors lead to extreme clinical heterogeneity, ranging from non-epileptic conditions to developmental and epileptic encephalopathy (DEE). This current study reports on findings from 343 patients referred by physicians in hospitals and tertiary care centers in Greece between 2017 and 2023. Positive family history for specific neurologic disorders was disclosed in 89 cases and the one common clinical feature was the onset of seizures, at a mean age of 17 months (range from birth to 15 years old). Most patients were specifically referred for SCN1A investigation (Sanger Sequencing and MLPA) and only five for next generation sequencing. Twenty-six SCN1A variants were detected, including nine novel causative variants (c.4567A>Τ, c.5564C>A, c.2176+2T>C, c.3646G>C, c.4331C>A, c.1130_1131delGAinsAC, c.1574_1580delCTGAGGA, c.4620A>G and c.5462A>C), and are herein presented, along with subsequent genotype–phenotype associations. The identification of novel variants complements SCN1A databases extending our expertise on genetic counseling and patient and family management including gene-based personalized interventions.

The objective of the study is to evaluate the evolving phenotype and genetic spectrum of patients with succinic semialdehyde dehydrogenase deficiency (SSADHD) in long-term follow-up. Longitudinal clinical and biochemical data of 22 pediatric and 9 adult individuals with SSADHD from the patient registry of the International Working Group on Neurotransmitter related Disorders (iNTD) were studied with in silico analyses, pathogenicity scores and molecular modeling of ALDH5A1 variants. Leading initial symptoms, with onset in infancy, were developmental delay and hypotonia. Year of birth and specific initial symptoms influenced the diagnostic delay. Clinical phenotype of 26 individuals (median 12 years, range 1.8-33.4 years) showed a diversifying course in follow-up: 77% behavioral problems, 76% coordination problems, 73% speech disorders, 58% epileptic seizures and 40% movement disorders. After ataxia, dystonia (19%), chorea (11%) and hypokinesia (15%) were the most frequent movement disorders. Involvement of the dentate nucleus in brain imaging was observed together with movement disorders or coordination problems. Short attention span (78.6%) and distractibility (71.4%) were the most frequently behavior traits mentioned by parents while impulsiveness, problems communicating wishes or needs and compulsive behavior were addressed as strongly interfering with family life. Treatment was mainly aimed to control epileptic seizures and psychiatric symptoms. Four new pathogenic variants were identified. In silico scoring system, protein activity and pathogenicity score revealed a high correlation. A genotype/phenotype correlation was not observed, even in siblings. This study presents the diversifying characteristics of disease phenotype during the disease course, highlighting movement disorders, widens the knowledge on the genotypic spectrum of SSADHD and emphasizes a reliable application of in silico approaches.

Background: The recently published WHO classification of central nervous system (CNS) tumours recognizes DNA methylation profiling as a desirable and, for some diagnoses, essential diagnostic tool adjunctive to conventional histopathology. DNA methylation profiling is not routinely available in many countries, including Greece. Methods: In this collaborative study, we report the DNA methylation results in a series of children and adolescents with CNS tumours in Greece (2018-2023). In total, 130 tumour samples were analyzed using the latest applicable version of the Heidelberg brain tumour classifier. Results: Upon initial analysis, 80 % (104/130) achieved calibrated scores (Cs) >= 0.9 and matched an established methylation class family/subclass. Among them, methylation results confirmed (90/104, 86.5 %), refined (50/104, 48 %) or changed (10/104, 9.6 %) the histological diagnosis. Only four results were regarded as non-contributing (4/104, 3.9 %). Twenty-six tumour samples received Cs < 0.9. Despite low scores, methylation results supported the initial diagnosis with lower confidence in 38.5 % (10/26) and established the diagnosis in two tumours with non-conclusive histopathology. Additional t-distributed stochastic neighbour embedding (t-SNE) analysis allowed the possible classification of twelve tumours. Nine more samples reached high Cs using the newer brain tumour classifiers, since available. Samples co-tested in Greece demonstrated excellent test reproducibility, supporting the analysis' local implementation. Methylome profiling impacted the clinical management of 40 % of patients, modifying stratification, prognosis, or treatment approach. Conclusions: This study supports the need to integrate methylome analysis into routine diagnostics in our country and highlights the importance of collaboration between European pediatric oncology centres.