PURPOSE:We aimed to define the clinical and genetic basis of an autosomal recessive neurodevelopmental disorder identified in 3 unrelated families with an overlapping multisystem phenotype. METHODS:Exome or genome sequencing was performed in 6 affected individuals from 3 families, revealing biallelic variants in SUPT4H1. Functional effects were evaluated using CRISPR and RNAi knockdown in C. elegans. Transcriptomic and proteomic profiling were conducted on patient-derived fibroblasts. Phylogenetic profiling assessed evolutionary conservation and coevolution. Dopamine response was evaluated in 2 affected siblings. RESULTS:All individuals carried biallelic SUPT4H1 variants-1 frameshift and 2 missense variants. Shared features included intellectual disability, dystonia, speech impairment, craniofacial dysmorphism, skeletal anomalies, and enamel hypoplasia. Functional modeling in C. elegans confirmed pathogenicity through neuromotor deficits. Multiomics analyses revealed dysregulation of developmental gene networks and the transcriptional machinery with disrupted RNA polymerase complexes and cell-cycle regulators. Dopamine treatment improved motor symptoms and normalized cerebrospinal neurotransmitter levels in 2 siblings. CONCLUSION:Biallelic variants in SUPT4H1 cause a previously unrecognized multisystem neurodevelopmental disorder. These findings underscore the importance of disrupted transcription in human disease and demonstrate how integrated multiomics and cross-species modeling can reveal underlying mechanisms and provide a foundation for future studies of transcriptional regulation.

To evaluate the baseline and follow-up clinical and radiological characteristics of a paediatric cohort initially diagnosed with isolated congenital growth hormone deficiency (IGHD) and pituitary morphology abnormality in MRI. Observational, ambispective and longitudinal review of paediatric patients with an initial diagnosis of growth hormone deficiency with pituitary morphology abnormality in MRI followed-up in a single tertiary hospital. After mean 11.3 (± 3.5DS) years of follow-up, the thirty patients (20 males) were classified into two groups: (1) isolated congenital growth hormone deficiency (IGHD) with 24 patients (9.5 years median follow up), and (2) combined pituitary hormone deficiencies (CPHD) with 6 patients (13.5 years median follow up). Median age at diagnosis was IGHD 3.0 [2.0–4.0] and CPHD 3.0 [1.5–5.2] years. Regarding the cerebral MRI scan results, 2 patients had septo-optic dysplasia (CPHD), 5 had pituitary stalk interruption syndrome (3 IGHD), one had ectopic posterior pituitary (IGHD), 16 had anterior pituitary hypoplasia (15 IGHD) and 6 had the latter two conditions combined (5 IGHD). In genetic studies, 1 of 25 patients had positive NGS panel results and it was in the IGHD group. The target gene detected was GLI2. Clinical exome sequencing was performed with six patients, yielding inconclusive results (1 in the IGHD group and 5 in the CPHD group). Array CGH was performed with eight patients (4 in the IGHD group and 4 in the CPHD group) and was negative in all patients. In the CPHD group, associated deficiencies begin to appear after 5 years [4.0–6.0] median follow-up, with thyrotropin being the most frequent (80

Objective: To assess whether targeted magnetic resonance of one or both of the progenitors could refine the diagnosis in cases of fetal brain anomalies with uncertain prognosis. Methods: Single-center retrospective case series, where targeted magnetic resonance was performed on one or both of progenitors after a suspicion of fetal complex brain anomalies, and prognosis was unclear based solely on fetal tests (neurosonogram, fetal magnetic resonance, and genetic testing). Results: Seven women were included. Results were relevant for prenatal counseling in five cases, with a definitive diagnosis in three: one periventricular nodular heterotopia, one mild tubulinopathy, and one dynein-associated neurodevelopmental disorder. Median gestational age at referral was 28.3 weeks (range, 20.7-34.9). Neurosonogram findings were inconclusive in all cases. Exome sequencing in amniotic fluid was conducted for all cases. Fetal magnetic resonance was performed at a median gestational age of 34.4 weeks (range, 29.3-35.7), confirming ultrasound diagnosis in all cases, and providing substantial additional information in two (2/7, 28.6%). Parental magnetic resonance findings aligned with fetal findings in 5/7 cases (71.4%). Conclusion: DUO or TRIO magnetic resonance, involving both progenitors and the fetus, could play a significant role in prenatal diagnosis of selected brain anomalies with uncertain prognosis.

Noonan syndrome and related disorders are a group of well-known genetic conditions caused by dysregulation of the Ras/mitogen-activated protein kinase (RAS/MAPK) pathway. Because of the overlap of clinical and molecular features, they are now called RASopathies. In this study, we retrospectively analyzed the clinical data of 121 patients with a molecularly confirmed diagnosis of RASopathy, describing frequencies for clinical features in all organ systems as well as molecular data. The most common clinical diagnosis was Noonan Syndrome and the most frequently affected gene was PTPN11 followed by SOS1, RAF1, LZTR1, and RIT1. All patients had distinctive craniofacial features indicative of the RASopathy spectrum but we report some atypical features regarding craniofacial shape, such as craniosynostosis and microcephaly. We also describe uncommon clinical characteristics such as aortic dilation, multivalvular heart disease, abnormalities of the posterior fossa, and uterine congenital anomalies in female patients. Furthermore, the presence of multiple giant cell granulomas was observed specifically in patients with SOS1 variants. This comprehensive evaluation allows broadening the phenotypic spectrum of our population and their correlation with the genotype, which are essential to improve the recognition and the follow up of RASopathies as a multisystemic disease.

The stalked barnacle Pollicipes pollicipes is an important economic resource in Portugal and Spain. Two extreme phenotypes can be identified, based on their morphology. More elongated barnacles are associated with bad quality and have a lower commercial value. The fishers perception about the existence, definition and causes for this phenotypical/quality variation was evaluated through a survey performed in Portugal and Galicia, Spain. The existence of two extreme commercial qualities was validated. Good quality barnacles were mainly defined as thick and short in both countries. In Spain (Galicia), the definition of bad quality animals corresponded mainly to the terms long and thin, while in Portugal, fishers used a wider variety of terms including watery, thin and soft. The characteristics of the rock and the hydrodynamics were the causes most referred by the fishers for this variation. The morphological variation of P. pollicipes was described by the ratio between maximal rostro-carinal length (RC) and total height (TH): RC/TH values > 0.4 indicate good quality barnacles; and values < 0.4 indicate bad quality barnacles. Although morphological variation between the two extreme qualities/phenotypes was found, no genetic (amplified fragment length polymorphism - AFLP) or epigenetic (methylation sensitive amplification polymorphism - MSAP) differences were detected.

Purpose Despite ever-increasing knowledge of the genetic etiologies of neurodevelopmental disorders, approximately half remain undiagnosed after exome or genome sequencing. Here, we provide a deep clinical characterization of 11 previously unreported patients with a recently described neurodevelopmental disorder (NDD) due to pathogenic variants in RNU4-2. Methods The 11 patients were identified in a pool of 70 patients selected for targeted RNU4-2 sequencing on the basis of their clinical phenotypes from a cohort of 1032 individuals with a NDD and without a prior genetic diagnosis. Results The 11 patients were aged between 13 months and 36 years. All patients showed moderate to severe developmental delay and/or intellectual disability. Height and weight were below 10th percentile and most showed microcephaly. In almost 50% of the patients, intrauterine growth retardation was detected. All patients showed a distinctive pattern of dysmorphic features, including hooded upper eyelid and epicanthus, full cheeks, tented philtrum, mouth constantly slightly open with an everted lower lip vermilion, high palate, and profuse drooling. Of 11 patients, 64% also presented with ophthalmological problems (mainly strabismus, nystagmus, and refraction errors) and 64% had musculoskeletal features (joint hypermobility, mild scoliosis, and easy fractures). Conclusion This work provides an improved characterization of the phenotypic spectrum of RNU4-2 syndrome across different age groups and demonstrates that thorough clinical assessment of patients with an NDD can be enhanced significantly for this novel syndrome.

En este trabajo se han utilizado 4 loci microsatélites para hacer una caracterización genética de los dos primeros lotes de individuos de la especie Litopenaeus vannamei introducidos en Cuba para el cultivo y para valorar también, desde el punto de vista genético, la posibilidad de crear un banco de reproductores a partir de estos lotes. Los resultados obtenidos indican niveles de variación genética (heterocigosidad media Ho=0,560, número medio de alelos Na=7,5) inferiores a los que previamente se han informado en otras poblaciones salvajes y de cultivo de la especie. Los niveles de relación genética entre individuos (grado de parentesco) son, al menos en uno de los lotes, significativamente altos (Lote 1 rmedia =-0.0080, Lote 2 rmedia =+0,1515). Se recomienda una estrategia de recopilación de la mayor variación genética posible, ya sea a partir de las poblaciones salvajes de origen de estos lotes de cultivo, ó a partir de cruzamientos entre lotes de origen común pero genéticamente diferentes. Para ello es necesario implementar herramientas como la crío-conservación de gametos y el genotipado con loci microsatélites para evitar cruzamientos entre individuos emparentados y seguir la heredabilidad de caracteres de interés para el cultivo.

Abstract Background Pituitary adenomas (PPAs) are uncommon in childhood and adolescence, accounting for 2–6% of all intracranial neoplasms. Delayed puberty, growth retardation, galactorrhea and weight gain are common features at presentation in pediatric patients. Functional tumors constitute a vast majority (90%) of PPAs, with the most frequent being prolactinomas. Case presentation A retrospective review of the clinical features and outcomes of 7 pediatric patients with pituitary macroadenomas was conducted. We included PPAs in patients under 18 years at diagnosis with diameters larger than 10 mm by magnetic resonance (MRI). Six patients were males (85%), with age at diagnosis ranging from 8 to 15 (median 14 ± 2.8SDS). The primary symptoms that led to medical attention were growth retardation, gigantism and secondary amenorrhea. The visual field was reduced in three cases (42%). Suprasellar extension was present in 3 subjects, and one had a giant adenoma. Adenomas were clinically functioning in 6 patients (85%) (three prolactinomas, two somatropinomas, one secreting FSH and one no-producer). The prolactinomas responded to treatment with cabergoline. For the rest, one required transsphenoidal surgery and the other three both surgery and radiotherapy. All patients undergoing radiotherapy had secondary panhypopituitarism. In relation to the genetic studies, two patients presented a pathogenic mutation of the AIP gene and one of the MEN1. Discusion and conclusion Pediatric pituitary macroadenomas are a distinct entity, mostly found in males and with a predominance of functional tumors leading to detrimental effects on growth and puberty in addition to neuro-ophthalmological manifestations. It is important to perform genetic studies in patients with macroadenomas appearing under the age of 18 years as genetic and syndromic associations are more frequent in this age group.

Shellfisheries of the intertidal and shallow subtidal infaunal bivalves Ruditapes decussatus, Ruditapes philippinarum, Venerupis corrugata and Cerastoderma edule are of great socio-economic importance (in terms of landings) in Europe, specifically in the Galician Rías Baixas (NW Spain). However, ocean warming may threaten these fisheries by modifying the geographic distribution of the species and thus affecting productive areas. The present study analysed the impact of rising ocean temperature on the geographical distribution of the thermal comfort areas of these bivalves throughout the 21st century. The Delft3D model was used to downscale climate data from CORDEX and CMIP5 and was run for July and August in three future periods (2025-2049, 2050-2074 and 2075-2099) under the RCP8.5 scenario. The areas with optimal temperature conditions for shellfish harvesting located in the middle and outer parts of the rias may increase in the near future for R. decussatus, V. corrugata and C. edule and decrease in the far future for R. philippinarum. Moreover, shellfish beds located in the shallower areas of the inner parts of the Rías Baixas could be affected by increased water temperature, reducing the productive areas of the four species by the end of the century. The projected changes in thermal condition will probably lead to changes in shellfish harvesting modality (on foot or aboard vessels) with further socio-economic consequences.

Increased heavy rainfall can reduce salinity to values close to 0 in estuaries. Lethal and sublethal physiological and behavioural effects of decreases in salinity below ten have already been found to occur in the commercially important clam species Venerupis corrugata, Ruditapes decussatus and R. philippinarum and the cockle Cerastoderma edule, which generate an income of ∼74 million euros annually in Galicia (NW Spain). However, studies of the molecular response to hyposaline stress in bivalves are scarce. This ‘shotgun’ proteomics study evaluates changes in mantle-edge proteins subjected to short-term hyposaline episodes in two different months (March and May) during the gametogenic cycle. We found evidence that the mantle-edge proteome was more responsive to sampling time than to hyposalinity, strongly suggesting that reproductive stages condition the stress response. However, hyposalinity modulated proteome profiles in V. corrugata and C. edule in both months and R. philippinarum in May, involving proteins implicated in protein folding, redox homeostasis, detoxification, cytoskeleton modulation and the regulation of apoptotic, autophagic and lipid degradation pathways. However, proteins that are essential for an optimal osmotic stress response but which are highly energy demanding, such as chaperones, osmoprotectants and DNA repair factors, were found in small relative abundances. In both months in R. decussatus and in March in R. philippinarum, almost no differences between treatments were detected. Concordant trends in the relative abundance of stress response candidate proteins were also obtained in V. corrugata and C. edule in the different months, but not in Ruditapes spp., strongly suggesting that the osmotic stress response in bivalves is complex and possibly influenced by a combination of controlled (sampling time) and uncontrolled variables. In this paper, we report potential molecular targets for studying the response to osmotic stress, especially in the most osmosensitive native species C. edule and V. corrugata, and suggest factors to consider when searching for biomarkers of hyposaline stress in bivalves.

Background: Acute myeloid leukemia (AML) is a malignant heterogeneous group of hematological diseases that originates from a hematopoietic progenitor with altered maturation capacity. Recently, considerable advances have been made in the development of targeted therapies for distinct molecularly defined subtypes. Although many AML patients initially respond to current treatment, the majority of them relapse. Therefore, new targeted therapies are needed to overcome drug resistance and improve treatment effectiveness. CXCR4 is a chemokine receptor that is expressed in over 20 cancer types, both hematologic cancers and solid tumors. CXCR4 receptor and its ligand CXCL12 are key mediators of the interactions between AML cells and the bone marrow (BM) microenvironment. Moreover, CXCR4 is highly expressed in around 50% of AML patients. Thus, we have generated a nanoparticle (T22-PE24-H6) that selectively delivers the exotoxin A from Pseudomonas aeruginosa to CXCR4+ leukemic cells. Aims: To assess the selectivity of T22-PE24-H6 cytotoxicity in CXCR4+ AML cell lines as well as in BM samples from AML patients. In addition, we evaluated the antineoplastic effect of the nanoparticle in a CXCR4+ AML disseminated mouse model. Methods: OCI-AML-3, MONO-MAC-6 and HEL cell lines were characterized for CXCR4 expression using flow cytometry and immunohistochemistry (IHC). The in vitro antineoplastic effect of T22-PE24-H6 was determined by cell viability assays. Competition assays with the CXCR4 antagonist AMD3100 were performed to demonstrate the CXCR4-dependent cytotoxicity of the nanoparticle. In vivo effect was assessed in NSG mice intravenously injected with 1x106 luminescent MONO-MAC-6 cells. Animals were treated with 5 μg T22-PE24-H6 or Buffer (166 mM NaCO3H pH 8) daily for 10 doses. Bioluminescence signal (BLI) was monitored to quantitatively measure and evaluate in vivo disease progression. Animal tissue samples were collected after mice euthanasia and used to analyze AML dissemination and toxicity. CXCR4 expression levels and T22-PE24-H6 effect were also determined in BM samples from 10 newly-diagnosed AML patients. Results: T22-PE24-H6 nanoparticle demonstrated a potent in vitro anticancer effect in MONO-MAC-6 cell line. The specific cytotoxic activity of the nanoparticle was CXCR4 dependent as demonstrated by performing competition assays with AMD3100. Furthermore, T22-PE24-H6 intravenous administrations showed significant BLI reduction in a CXCR4+ AML disseminated mouse model compared to buffer-treated mice. In addition, no differences between groups in mouse body weight, biochemical parameters or histopathological changes in normal tissues were detected. Finally, T22-PE24-H6 causes a significant cell viability reduction in AML patient samples with high CXCR4 expression. In contrast, the nanoparticle has no effect in AML patient samples with low expression of CXCR4. Summary/Conclusion: T22-PE24-H6 selectively kills AML cell lines and BM samples from AML patients with CXCR4 overexpression. The nanoparticle also induces a high antineoplastic effect in a CXCR4+ AML disseminated mouse model without detectable systemic toxicity. These data strongly support that T22-PE24-H6 may obtain therapeutic benefit for AML patients with high CXCR4 expression.

Purpose Changes in the myocardial extracellular matrix (ECM) identified using T1 mapping cardiovascular magnetic resonance (CMR) have been only reported in obese adults, but with opposite conclusions. The objectives are to assess the composition of the myocardial ECM in an obese pediatric population without type 2 diabetes by quantifying native T1 time, and to quantify the pericardial fat index (PFI) and their relationship with cardiovascular risk factors. Methods Observational case-control research of 25 morbidly obese adolescents and 13 normal-weight adolescents. Native T1 and T2 times (ms), left ventricular (LV) geometry and function, PFI (g/ht(3)) and hepatic fat fraction (HFF, %) were calculated by 1.5-T CMR. Results No differences were noticed in native T1 between obese and non-obese adolescents (1000.0 vs. 990.5 ms, p0.73), despite showing higher LV mass values (28.3 vs. 22.9 g/ht(3), p0.01). However, the T1 mapping values were significantly higher in females (1012.7 vs. 980.7 ms, p < 0.01) while in males, native T1 was better correlated with obesity parameters, particularly with triponderal mass index (TMI) (r = 0.51), and inflammatory cells. Similarly, the PFI was correlated with insulin resistance (r = 0.56), highly sensitive C-reactive protein (r = 0.54) and TMI (r = 0.77). Conclusion Female adolescents possess myocardium peculiarities associated with higher mapping values. In males, who are commonly more exposed to future non-communicable diseases, TMI may serve as a useful predictor of native T1 and pericardial fat increases. Furthermore, HFF and PFI appear to be markers of adipose tissue infiltration closely related with hypertension, insulin resistance and inflammation.

Background and Objectives Genetic white matter disorders (GWMD) are of heterogeneous origin, with >100 causal genes identified to date. Classic targeted approaches achieve a molecular diagnosis in only half of all patients. We aimed to determine the clinical utility of singleton whole-exome sequencing and whole-genome sequencing (sWES-WGS) interpreted with a phenotype- and interactome-driven prioritization algorithm to diagnose GWMD while identifying novel phenotypes and candidate genes. Methods A case series of patients of all ages with undiagnosed GWMD despite extensive standard-of-care paraclinical studies were recruited between April 2017 and December 2019 in a collaborative study at the Bellvitge Biomedical Research Institute (IDIBELL) and neurology units of tertiary Spanish hospitals. We ran sWES and WGS and applied our interactome-prioritization algorithm based on the network expansion of a seed group of GWMD-related genes derived from the Human Phenotype Ontology terms of each patient. Results We evaluated 126 patients (101 children and 25 adults) with ages ranging from 1 month to 74 years. We obtained a first molecular diagnosis by singleton WES in 59% of cases, which increased to 68% after annual reanalysis, and reached 72% after WGS was performed in 16 of the remaining negative cases. We identified variants in 57 different genes among 91 diagnosed cases, with the most frequent being RNASEH2B, EIF2B5, POLR3A, and PLP1, and a dual diagnosis underlying complex phenotypes in 6 families, underscoring the importance of genomic analysis to solve these cases. We discovered 9 candidate genes causing novel diseases and propose additional putative novel candidate genes for yet-to-be discovered GWMD. Discussion Our strategy enables a high diagnostic yield and is a good alternative to trio WES/WGS for GWMD. It shortens the time to diagnosis compared to the classical targeted approach, thus optimizing appropriate management. Furthermore, the interactome-driven prioritization pipeline enables the discovery of novel disease-causing genes and phenotypes, and predicts novel putative candidate genes, shedding light on etiopathogenic mechanisms that are pivotal for myelin generation and maintenance.

Preterm newborns with germinal matrix-intraventricular hemorrhage (GM-IVH) are at a higher risk of evidencing neurodevelopmental alterations. Present study aimed to explore the long-term effects that GM-IVH have on hippocampal subfields, and their correlates with memory. The sample consisted of 58 participants, including 36 preterm-born (16 with GM-IVH and 20 without neonatal brain injury), and 22 full-term children aged between 6 and 15 years old. All participants underwent a cognitive assessment and magnetic resonance imaging study. GM-IVH children evidenced lower scores in Full Intelligence Quotient and memory measures compared to their low-risk preterm and full-term peers. High-risk preterm children with GM-IVH evidenced significantly lower total hippocampal volumes bilaterally and hippocampal subfield volumes compared to both low-risk preterm and full-term groups. Finally, significant positive correlations between memory and hippocampal subfield volumes were only found in preterm participants together; memory and the right CA-field correlation remained significant after Bonferroni correction was applied ( p = .002). In conclusion, memory alterations and both global and regional volumetric reductions in the hippocampus were found to be specifically related to a preterm sample with GM-IVH. Nevertheless, results also suggest that prematurity per se has a long-lasting impact on the association between the right CA-field volume and memory during childhood.

Background: Between April and June 2016, an outbreak of rhomben-cephalitis (RE) caused by enterovirus (EV) A71 was detected in Catalonia, Spain-the first documented in Western Europe. The clinical characteristics and outcome of patients with this condition differed from those reported in outbreaks occurring in Southeast Asia. Methods: Observational, multicenter study analyzing characteristics, treatment and outcome of patients with EV-A71 rhombencephalitis diagnosed in 6 publicly funded hospitals within the Catalonian Health Institute. A review of clinical characteristics, diagnosis, treatment and outcome of these patients was conducted. Results: Sixty-four patients met the clinical and virologic criteria for rhombencephalitis caused by EV-A71. All patients had symptoms suggesting viral disease, mainly fever, lethargy, ataxia and tremor, with 30% of hand-foot-mouth disease. Intravenous immunoglobulin therapy was given to 44/64 (69%) patients and methylprednisolone to 27/64 (42%). Six patients (9%) required pediatric intensive care unit admission. Three patients had acute flaccid paralysis of 1 limb, and another had autonomic nervous system (ANS) dysfunction with cardiorespiratory arrest. Outcome in all patients (except the patient with hypoxic-ischemic encephalopathy) was good, with complete resolution of the symptoms. Conclusions: During the 2016 outbreak, rhombencephalitis without ANS symptoms was the predominant form of presentation and most patients showed no hand-foot-mouth disease. These findings contrast with those of other patient series reporting associated ANS dysfunction (10%-15%) and hand-foot-mouth disease (60%-80%). Complete recovery occurred in almost all cases. In light of the favorable outcome in untreated mild cases, therapies for this condition should be reserved for patients with moderatesevere infection. The main relevance of this study is to provide useful information for setting priorities, management approaches and adequate use of resources in future EV-A71 associated rhombencephalitis outbreaks.

The objective of this study is to determine whether hepatic artery Doppler ultrasound parameters can predict arterial complications in the immediate period after a liver transplantation in children.A retrospective review of the pediatric liver database at our tertiary-care pediatric hospital was performed. The study included 57 pediatric patients who underwent liver transplantation from 2016 to 2020. Clinical, laboratory and Doppler findings were recorded daily the first 5 days after transplantation. Especial attention was focused on extrahepatic post-anastomotic Peak Systolic Velocity (PSV) and intrahepatic Resistive Index (RI). Forty-nine liver transplant recipients were analyzed. Patients with acute hepatic artery complications, including acute thrombosis and stenosis, had lower PSV values at 3 and 4 days after surgery compared to the group with non-complications, with a statistical significance (p=.015). Receiver operating characteristic (ROC) curve analysis determined an optimal cut-off value of PSV less than 30 cm/s to discriminate children with and without acute hepatic arterial complications, which is lower than that proposed in adults. It correlates with acute arterial stenosis and thrombosis in children even before RI, clinical symptoms or laboratory anomalies appear.

The neurological phenotype of 3-hydroxyisobutyryl-CoA hydrolase (HIBCH) and short-chain enoyl-CoA hydratase (SCEH) defects is expanding and natural history studies are necessary to improve clinical management. From 42 patients with Leigh syndrome studied by massive parallel sequencing, we identified five patients with SCEH and HIBCH deficiency. Fourteen additional patients were recruited through collaborations with other centres. In total, we analysed the neurological features and mutation spectrum in 19 new SCEH/HIBCH patients. For natural history studies and phenotype to genotype associations we also included 70 previously reported patients. The 19 newly identified cases presented with Leigh syndrome (SCEH, n = 11; HIBCH, n = 6) and paroxysmal dystonia (SCEH, n = 2). Basal ganglia lesions (18 patients) were associated with small cysts in the putamen/pallidum in half of the cases, a characteristic hallmark for diagnosis. Eighteen pathogenic variants were identified, 11 were novel. Among all 89 cases, we observed a longer survival in HIBCH compared to SCEH patients, and in HIBCH patients carrying homozygous mutations on the protein surface compared to those with variants inside/near the catalytic region. The SCEH p.(Ala173Val) change was associated with a milder form of paroxysmal dystonia triggered by increased energy demands. In a child harbouring SCEH p.(Ala173Val) and the novel p.(Leu123Phe) change, an 83.6% reduction of the protein was observed in fibroblasts. The SCEH and HIBCH defects in the catabolic valine pathway were a frequent cause of Leigh syndrome in our cohort. We identified phenotype and genotype associations that may help predict outcome and improve clinical management.