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Thyroid dyshormonogenesis (THD) is a heterogeneous group of genetic diseases caused by the total or partial defect in the synthesis or secretion of thyroid hormones. Genetic variants in DUOX2 can cause partial to total iodination organification defects and clinical heterogeneity, from transient to permanent congenital hypothyroidism. The aim of this study was to undertake a molecular characterization and genotype-phenotype correlation in patients with THD and candidate variants in DUOX2. A total of 31 (19.38%) patients from the Catalan Neonatal Screening Program presented with variants in DUOX2 that could explain their phenotype. Fifteen (48.39%) patients were compound heterozygous, 10 (32.26%) heterozygous, and 4 (12.90%) homozygous. In addition, 8 (26.67%) of these patients presented variants in other genes. A total of 35 variants were described, 10 (28.57%) of these variants have not been previously reported in literature. The most frequent variant in our cohort was c.2895_2898del/p.(Phe966SerfsTer29), classified as pathogenic according to reported functional studies. The final diagnosis of this cohort was permanent THD in 21 patients and transient THD in 10, according to reevaluation and/or need for treatment with levothyroxine. A clear genotype-phenotype correlation could not be identified; therefore, functional studies are necessary to confirm the pathogenicity of the variants.
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Oxidasas Duales , Estudios de Asociación Genética , Humanos , Oxidasas Duales/genética , Oxidasas Duales/metabolismo , Femenino , Masculino , Recién Nacido , Disgenesias Tiroideas/genética , Disgenesias Tiroideas/patología , Fenotipo , Mutación , Genotipo , Hipotiroidismo Congénito/genética , Tamizaje Neonatal , TiroxinaRESUMEN
Introduction: Defects in any thyroid hormone synthesis steps cause thyroid dyshormonogenesis (THD). THD due to thyroglobulin (TG) gene variants is a cause of congenital hypothyroidism (CH) with a wide clinical spectrum, ranging from mild to severe permanent hypothyroidism. We present high-throughput sequencing results of patients with TG variants. Methods: A CH high-throughput sequencing-panel of the main genes involved in the regulation of thyroid hormonogenesis was performed to identify those TG variants that may be related to patient THD phenotype. Results: We identified 21 TG gene variants in 19 patients (11.8%) which could explain their phenotype. Ten of those (47.6%) were not previously described. CH was biochemically severe in these 19 patients. Eight of them were reevaluated after one month of discontinuing LT4 treatment and all had severe permanent hypothyroidism. We also identified another 16 patients who presented heterozygous TG variants, of whom, at reevaluation, five had mild permanent and only one had severe permanent hypothyroidisms. Discussions: In this study, 10 novel and 11 previously reported variants in the TG gene have been identified that could explain the phenotype of 19 patients from non-consanguineous families from a large THD cohort. Although not all these TG gene variants can explain all the patients' THD phenotypes, some of them had severe or mild permanent hypothyroidism at reevaluation.
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Hipotiroidismo Congénito , Tiroglobulina , Humanos , Tiroglobulina/genética , Femenino , Masculino , Hipotiroidismo Congénito/genética , Niño , Preescolar , Secuenciación de Nucleótidos de Alto Rendimiento , Fenotipo , Lactante , Disgenesias Tiroideas/genética , Mutación , Adolescente , Adulto , Recién NacidoRESUMEN
Palmoplantar keratoderma (PPK) is a multi-faceted skin disorder characterized by the thickening of the epidermis and abrasions on the palms and soles of the feet. Among the genetic causes, biallelic pathogenic variants in the FAM83G gene have been associated with PPK in dogs and humans. Here, a novel homozygous variant (c.794G>C, p.Arg265Pro) in the FAM83G gene, identified by whole exome sequencing in a 60-year-old female patient with PPK, is reported. The patient exhibited alterations in the skin of both hands and feet, dystrophic nails, thin, curly and sparse hair, long upper eyelid eyelashes, and poor dental enamel. FAM83G activates WNT signalling through association with ser/thr protein kinase CK1α. When expressed in FAM83G-/- DLD1 colorectal cancer cells, the FAM83GR265P variant displayed poor stability, a loss of interaction with CK1α and attenuated WNT signalling response. These defects persisted in skin fibroblast cells derived from the patient. Our findings imply that the loss of FAM83G-CK1α interaction and subsequent attenuation of WNT signalling underlie the pathogenesis of PPK caused by the FAM83GR265P variant.
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Caseína Quinasa Ialfa , Queratodermia Palmoplantar , Vía de Señalización Wnt , Humanos , Femenino , Queratodermia Palmoplantar/genética , Queratodermia Palmoplantar/patología , Persona de Mediana Edad , Caseína Quinasa Ialfa/metabolismo , Caseína Quinasa Ialfa/genética , Secuenciación del Exoma , Unión Proteica , Fibroblastos/metabolismoRESUMEN
Background/Objectives: Non-Invasive prenatal test (NIPT) is used as a universal or contingent test after prior risk assessment. Screening is mainly performed for common trisomies (T21, T13, T18), although other chromosomal anomalies may be detected. Our objective was to study the performance of GWNIPT in the detection of chromosomal abnormalities in pregnancies in which an invasive prenatal study was performed and in early pregnancy losses, in comparison with the reference test. Method: VeriSeqTM NIPT Solution v2, a genome-wide NIPT (GWNIPT), was performed prior to invasive testing in fetal diagnostic study cases (FDS, n = 155) and in early pregnancy losses (EPL, n = 68). Results: In the FDS group, the diagnostic test (QFPCR, array and karyotype) detected anomalies in 32 pregnancies (21%), in twenty of them (61%) also detected by GWNIPT. Eleven of the twelve cases undetected by GWNIPT were balanced translocations (n = 4) or deletions/duplications <7 Mb (n = 7). In the EPL group, GWNIPT detected anomalies in 46% of cases (31/68) but comparison with reference test (QFPCR and karyotype) in products of conception (POC) was only possible in 18 cases. Concordant results between POC and GWNIPT test were obtained in 16 of the 18 cases. In EPL, with GWNIPT testing, common trisomies accounted for 25.8% of cases (8/31), rare trisomies 54.8% (17/31) and microdeletions/duplications 16.1% (5/31). Conclusions: The GWNIPT test may be useful in clinical practice in prenatal and in EPL's genetic diagnosis when the appropriate sample is not available.
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Background: Previous studies found high but very variable levels of tetranor-PGEM and PGDM (urine metabolites of prostaglandin (PG) E2 and PGD2, respectively) in persons with cystic fibrosis (pwCF). This study aims to assess the role of cyclooxygenase COX-1 and COX-2 genetic polymorphisms in PG production and of PG metabolites as potential markers of symptoms' severity and imaging findings. Methods: A total of 30 healthy subjects and 103 pwCF were included in this study. Clinical and radiological CF severity was evaluated using clinical scoring methods and chest computed tomography (CT), respectively. Urine metabolites were measured using liquid chromatography/tandem mass spectrometry. Variants in the COX-1 gene (PTGS1 639 C>A, PTGS1 762+14delA and COX-2 gene: PTGS2-899G>C (-765G>C) and PTGS2 (8473T>C) were also analyzed. Results: PGE-M and PGD-M urine concentrations were significantly higher in pwCF than in controls. There were also statistically significant differences between clinically mild and moderate disease and severe disease. Patients with bronchiectasis and/or air trapping had higher PGE-M levels than patients without these complications. The four polymorphisms did not associate with clinical severity, air trapping, bronchiectasis, or urinary PG levels. Conclusions: These results suggest that urinary PG level testing can be used as a biomarker of CF severity. COX genetic polymorphisms are not involved in the variability of PG production.
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Objectives: Thymidine kinase 2 deficiency (TK2d) is a rare autosomal recessive disorder that stems from a perturbation of the mitochondrial DNA maintenance. Nucleoside treatment has recently shown promise as a disease-modifying therapy. TK2d was initially associated with rapidly progressive fatal myopathy in children featuring mitochondrial DNA depletion. Subsequently, less severe variants of the disease were described, with onset of symptoms during adolescence or adulthood and associated with the presence of multiple mtDNA deletions. These less severe phenotypes have been reported in only 15% of the approximately 120 patients described worldwide. However, some reports suggest that these juvenile and adult-onset presentations may be more common. The objective of this study was to describe the clinical phenotype in a sample of patients from Spain. Methods: This study includes 53 patients harboring biallelic TK2 pathogenic variants, compiling data retrospectively from 7 Spanish centers. We analyzed allele frequency, investigated the most recent common ancestor of core haplotypes, and used the Runs of Homozygosity approach to investigate variant coalescence. Results: Symptom onset distribution revealed that 32 patients (60%) experienced symptoms beyond 12 years of age. Approximately 30% of patients died of respiratory insufficiency, while 56% of surviving patients needed mechanical ventilation. Genetic analysis identified 16 distinct variants in TK2. Two variants, p.Lys202del and p.Thr108Met, exhibited significantly higher prevalence in the Spanish population than that reported in gnomAD database (86-fold and 13-fold, respectively). These variants are estimated to have originated approximately 16.8 generations ago for p.Thr108Met and 95.2 generations ago for p.Lys202del within the Spanish population, with the increase in frequency attributed to various forms of inbreeding. In late-onset cases, 46.9% carried the p.Lys202del variant. Discussion: The higher frequency of TK2d in Spain can be partially attributed to the increased prevalence of 2 variants and consanguinity. Notably, in 60% of the cohort, the disease was late-onset, emphasizing the potential underdiagnosis of this subgroup of patients in other regions. Raising awareness of this potentially treatable disorder is of utmost importance because early interventions can significantly affect the quality of life and survival of affected individuals.
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Tuberous sclerosis complex (TSC) is an autosomal dominant genetic disorder characterized by the presence of hamartomas in multiple organs. At the molecular level, the disease is caused by pathogenic variants in the TSC1 and TSC2 genes, and only 10% to 25% of clinically diagnosed patients remain negative after multiplex ligation-dependent probe amplification and exon sequencing of both genes. Here, to improve the molecular diagnosis of TSC, we developed an integral approach that includes multiplex ligation-dependent probe amplification and deep-coverage next-generation sequencing of the entire TSC1 and TSC2 genes, along with an adapted bioinformatic pipeline to detect variants at low allele frequencies (>1%). Using this workflow, the molecular cause was identified in 29 of 42 patients with TSC, describing here, for the first time, 12 novel pathogenic variants in TSC genes. These variants included seven splicing variants, five of which were studied at the cDNA level, determining their effect on splicing. In addition, 8 of the 29 pathogenic variants were detected in mosaicism, including four patients with previous negative study results who presented extremely low mosaic variants (allele frequency, <16%). We demonstrate that this integral approach allows the molecular diagnosis of patients with TSC and improves the conventional one by adapting the technology to the detection of low-frequency mosaics.
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Mosaicismo , Esclerosis Tuberosa , Humanos , Proteína 2 del Complejo de la Esclerosis Tuberosa/genética , Proteína 1 del Complejo de la Esclerosis Tuberosa/genética , Mutación , Esclerosis Tuberosa/diagnóstico , Esclerosis Tuberosa/genéticaRESUMEN
CONTEXT: Patients with congenital hyperinsulinism due to ABCC8 variants generally present severe hypoglycemia and those who do not respond to medical treatment typically undergo pancreatectomy. Few data exist on the natural history of non-pancreatectomized patients. OBJECTIVE: This work aims to describe the genetic characteristics and natural history in a cohort of non-pancreatectomized patients with congenital hyperinsulinism due to variants in the ABCC8 gene. METHODS: Ambispective study of patients with congenital hyperinsulinism with pathogenic or likely pathogenic variants in ABCC8 treated in the last 48 years and who were not pancreatectomized. Continuous glucose monitoring (CGM) has been periodically performed in all patients since 2003. An oral glucose tolerance test was performed if hyperglycemia was detected in the CGM. RESULTS: Eighteen non-pancreatectomized patients with ABCC8 variants were included. Seven (38.9%) patients were heterozygous, 8 (44.4%) compound heterozygous, 2 (11.1%) homozygous, and 1 patient carried 2 variants with incomplete familial segregation studies. Seventeen patients were followed up and 12 (70.6%) of them evolved to spontaneous resolution (median age 6.0 ± 4 years; range, 1-14). Five of these 12 patients (41.7%) subsequently progressed to diabetes with insufficient insulin secretion. Evolution to diabetes was more frequent in patients with biallelic variants in the ABCC8 gene. CONCLUSION: The high remission rate observed in our cohort makes conservative medical treatment a reliable strategy for the management of patients with congenital hyperinsulinism due to ABCC8 variants. In addition, a periodic follow-up of glucose metabolism after remission is recommended, as a significant proportion of patients evolved to impaired glucose tolerance or diabetes (biphasic phenotype).
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Hiperinsulinismo Congénito , Diabetes Mellitus , Niño , Preescolar , Humanos , Glucemia , Automonitorización de la Glucosa Sanguínea , Hiperinsulinismo Congénito/complicaciones , Hiperinsulinismo Congénito/genética , Hiperinsulinismo Congénito/cirugía , Diabetes Mellitus/etiología , Diabetes Mellitus/genética , Hiperinsulinismo/genética , Mutación , Receptores de Sulfonilureas/genética , Pancreatectomía/efectos adversosRESUMEN
TANGO2-related disease is an autosomal recessive multisystem disease associated with developmental delay and infancy-onset recurrent metabolic crises with early mortality. Several studies have reported dysfunction in endoplasmic reticulum-to-Golgi traffic and mitochondrial homoeostasis as the underlying pathophysiology. We report a 40-year-old woman affected by limb-girdle weakness and mild intellectual disability caused by the recurrent deletion of exons 3-9 in homozygosity in the TANGO2 gene. Physical examination revealed hyperlordosis, waddling gait, calf pseudohypertrophy, and Aquilian tendon retractions. Laboratory investigations revealed elevation of serum biomarkers suggestive of mitochondrial dysfunction together with hypothyroidism. At the age of 24, the patient suffered a metabolic crisis with severe rhabdomyolysis and malignant cardiac arrhythmia. After recovery, no metabolic or arrhythmic crisis has recurred. Muscle histology two years later revealed increased endomysial fibrosis and other myopathic changes. Our findings illustrate the mildest end of the phenotypic spectrum of TANGO2-related disease and reveal further aspects related to chronic muscle damage in this disorder.
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Discapacidad Intelectual , Enfermedades Musculares , Rabdomiólisis , Femenino , Humanos , Adulto , Discapacidad Intelectual/diagnóstico , Discapacidad Intelectual/genética , Enfermedades Musculares/diagnóstico , Enfermedades Musculares/genética , Enfermedades Musculares/patología , Exones , Rabdomiólisis/genética , HomocigotoRESUMEN
RRM2B encodes the p53-inducible small subunit (p53R2) of ribonucleotide reductase, a key protein for mitochondrial DNA (mtDNA) synthesis. Pathogenic variants in this gene result in familial mitochondrial disease in adults and children, secondary to a maintenance disorder of mtDNA. This study describes two patients, mother and son, with early-onset chronic progressive external ophthalmoplegia (PEO). Skeletal muscle biopsy from the latter was examined: cytochrome c oxidase (COX)-negative fibres were shown, and molecular studies revealed multiple mtDNA deletions. A next-generation sequencing gene panel for nuclear-encoded mitochondrial maintenance genes identified two unreported heterozygous missense variants (c.514 G > A and c.682 G > A) in the clinically affected son. The clinically affected mother harboured the first variant in homozygous state, and the clinically unaffected father harboured the remaining variant in heterozygous state. In silico analyses predicted both variants as deleterious. Cell culture studies revealed that patients' skin fibroblasts, but not fibroblasts from healthy controls, responded to nucleoside supplementation with enhanced mtDNA repopulation, thus suggesting an in vitro functional difference in patients' cells. Our results support the pathogenicity of two novel RRM2B variants found in two patients with autosomal recessive PEO with multiple mtDNA deletions inherited with a pseudodominant pattern.
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Oftalmoplejía Externa Progresiva Crónica , Oftalmoplejía , Ribonucleótido Reductasas , Adulto , Niño , Humanos , Oftalmoplejía Externa Progresiva Crónica/genética , Oftalmoplejía Externa Progresiva Crónica/patología , Patrón de Herencia , ADN Mitocondrial/genética , Ribonucleótido Reductasas/genética , Proteínas de Ciclo Celular/genéticaRESUMEN
BACKGROUND: Consanguineous couples have an increased risk of severe diseases in offspring due to autosomal recessive disorders. Exome sequencing (ES) offers the possibility of extensive preconception carrier screening (PCS) in consanguineous couples who may be at risk of rare genetic disorders. METHODS: We retrospectively analysed ES data from 65 probands affected with rare genetic disorders born from consanguineous couples. We explored diagnostic yield and carrier status for recessive disorders. RESULTS: The overall diagnostic yield in a singleton approach was 53.8%, mostly recessive variants. In a hypothetical exome-based PCS, only 11.7% of these causative rare variants would have been missed in the filtering process. Carrier screening for recessive conditions allowed the identification of at least one additional pathogenic or likely pathogenic variant in 85.7% of the probands, being the majority with a gene carrier frequency <1 in 200. In addition, considering only clinically actionable conditions, we estimated that 12.3% of our close consanguineous couples may be at risk for an additional recessive disease. CONCLUSIONS: Our results demonstrate that ES outperforms panel-based screening in a PCS context in consanguineous couples and could potentially increase their reproductive autonomy and facilitate informed decision-making.
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Enfermedades Raras , Humanos , Consanguinidad , Secuenciación del Exoma , Estudios Retrospectivos , Genes Recesivos , Frecuencia de los Genes , Enfermedades Raras/genética , Tamización de Portadores GenéticosRESUMEN
BACKGROUND/OBJECTIVES: Exome sequencing may identify pathogenic variants unrelated with the purpose of the analysis. We investigated the frequency of secondary and incidental findings (SF/IF) in cancer susceptibility genes (CSG), their clinical actionability and the psychological impact in individuals with an SF/IF (cases) compared with individuals tested due to their cancer history (controls). METHODS: This study analysed 533 exomes ordered for non-cancer conditions. Medical records were reviewed for clinical actionability of SF/IF. Psychological impact was analysed using the Multidimensional Impact of Cancer Risk Assessment (MICRA) scale and compared between cases and controls with a propensity score weighting method. RESULTS: The frequency of SF/IF in CSG was 2.1% (95% CI 1.1% to 3.8%): three BRCA2, three PMS2, two SDHB, and one each in BRCA1, MLH1 and RAD51C. Among the relatives, 18 were carriers. Twenty enrolled for surveillance, and a neoplasm was diagnosed in 20%: three paragangliomas and one breast cancer. Cases presented higher MICRA mean scores than controls (21.3 vs 16.2 in MICRA total score, 6.3 vs 4.2 in the distress subscale, and 8.3 vs 6.6 in the uncertainty subscale; all p<0.001). CONCLUSION: SF/IF in CSG were identified in 2.1% of patients. Despite a numerically higher psychological impact, the identification of SF/IF allowed early detection and cancer prevention in families without cancer history.
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Neoplasias de la Mama , Predisposición Genética a la Enfermedad , Humanos , Femenino , Secuenciación del Exoma , Hallazgos Incidentales , Neoplasias de la Mama/genética , Genes BRCA2RESUMEN
Clinical exome sequencing has the potential to identify pathogenic variants unrelated to the purpose of the study (secondary findings, SFs). Data describing actual choices of SFs in participants in a clinical setting and factors influencing their decision are virtually non-existant in Europe. In this work, we report the acceptance rate of SFs, calculate their prevalence and study factors associated with the decision in a cohort of patients affected with a rare genetic disorder in a Spanish Hospital. Finally, we re-examine the presence of previously non reported family history in positive cases. We retrospectively reviewed informed consent choices and SF results from 824 unrelated probands affected with rare genetic disorders who underwent whole-genome or exome sequencing. Ninety percent of families (740/824) affected with rare disorders wished to be informed of SFs. Declining SFs was associated with a prenatal setting (30% vs. 8.7%, p = 0.025), consanguinity (19% vs. 8.7%, p = 0.013), male gender (10.6% vs. 1.5%, p = 0.00865) and the proband being a minor (10.6% vs. 1.5%, p = 0.014). Overall, 27 pathogenic or likely pathogenic variants were identified in 27 individuals, with an SF prevalence of 3.6%. Disclosure of SFs increased the percentage of positive family histories and resulted in early diagnosis or changes in the management of 10 individuals from five families. We show that the acceptance of SFs in Spain is high and the disclosure of SFs leads to a clinically meaningful change in the medical management of individuals.
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Revelación , Familia , Humanos , Masculino , Estudios Retrospectivos , Prevalencia , Secuenciación del ExomaRESUMEN
Chronic progressive external ophthalmoplegia (CPEO) plus syndrome due to pathogenic biallelic variants in TOP3A gene has been described in only one single patient. We report two adult siblings with c.614A>G (p.Asp205Gly) homozygous missense variant in the TOP3A gene who had CPEO plus syndrome.
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Oftalmoplejía Externa Progresiva Crónica , Oftalmoplejía , Adulto , Humanos , Oftalmoplejía Externa Progresiva Crónica/genética , Oftalmoplejía Externa Progresiva Crónica/patología , Mutación Missense , Homocigoto , Oftalmoplejía/genética , ADN Mitocondrial/genéticaRESUMEN
Methods to reconstruct the mitochondrial DNA (mtDNA) sequence using short-read sequencing come with an inherent bias due to amplification and mapping. They can fail to determine the phase of variants, to capture multiple deletions and to cover the mitochondrial genome evenly. Here we describe a method to target, multiplex and sequence at high coverage full-length human mitochondrial genomes as native single-molecules, utilizing the RNA-guided DNA endonuclease Cas9. Combining Cas9 induced breaks, that define the mtDNA beginning and end of the sequencing reads, as barcodes, we achieve high demultiplexing specificity and delineation of the full-length of the mtDNA, regardless of the structural variant pattern. The long-read sequencing data is analysed with a pipeline where our custom-developed software, baldur, efficiently detects single nucleotide heteroplasmy to below 1%, physically determines phase and can accurately disentangle complex deletions. Our workflow is a tool for studying mtDNA variation and will accelerate mitochondrial research.
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Genoma Mitocondrial , ADN Mitocondrial/genética , Desoxirribonucleasa I/genética , Genoma Humano/genética , Genoma Mitocondrial/genética , Secuenciación de Nucleótidos de Alto Rendimiento/métodos , Humanos , Nucleótidos , ARN , Análisis de Secuencia de ADN/métodosRESUMEN
Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease that can rarely affect young individuals. Juvenile ALS (JALS) is defined for individuals with an onset of the disease before the age of 25. The contribution of genetics to ALS pathology is a field of growing interest. One of the differences between adult-onset ALS and JALS is their genetic background, with a higher contribution of genetic causes in JALS. We report a patient with JALS and a pathogenic variant in the TARDBP gene (c.1035C > G; p.Asn345Lys), previously reported only in adult-onset ALS, and with an atypical phenotype of marked upper motor neuron predominance. In addition, the proband presented an additional variant in the NEK1 gene, c.2961C > G (p.Phe987Leu), which is classified as a variant of unknown significance. Segregation studies showed a paternal origin of the TARDBP variant, while the variant in NEK1 was inherited from the mother. We hypothesize that the NEK1 variant acts as a disease modifier and suggests the possibility of a functional interaction between both genes in our case. This hypothesis could explain the peculiarities of the phenotype, penetrance, and the age of onset. This report highlights the heterogeneity of the phenotypic presentation of ALS associated with diverse pathogenic genetic variants.
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Esclerosis Amiotrófica Lateral , Enfermedades Neurodegenerativas , Esclerosis Amiotrófica Lateral/genética , Esclerosis Amiotrófica Lateral/patología , Humanos , Neuronas Motoras/patología , Enfermedades Neurodegenerativas/patología , Penetrancia , FenotipoRESUMEN
The quantification of mitochondrial respiratory chain (MRC) enzymatic activities is essential for diagnosis of a wide range of mitochondrial diseases, ranging from inherited defects to secondary dysfunctions. MRC lesion is frequently linked to extended cell damage through the generation of proton leak or oxidative stress, threatening organ viability and patient health. However, the intrinsic challenge of a methodological setup and the high variability in measuring MRC enzymatic activities represents a major obstacle for comparative analysis amongst institutions. To improve experimental and statistical robustness, seven Spanish centers with extensive experience in mitochondrial research and diagnosis joined to standardize common protocols for spectrophotometric MRC enzymatic measurements using minimum amounts of sample. Herein, we present the detailed protocols, reference ranges, tips and troubleshooting methods for experimental and analytical setups in different sample preparations and tissues that will allow an international standardization of common protocols for the diagnosis of MRC defects. Methodological standardization is a crucial step to obtain comparable reference ranges and international standards for laboratory assays to set the path for further diagnosis and research in the field of mitochondrial diseases.
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AIM: To correlate clinical, radiological, and biochemical features with genetic findings in children with bilateral basal ganglia lesions of unknown aetiology, and propose a diagnostic algorithm for early recognition. METHOD: Children with basal ganglia disease were recruited in a 2-year prospective multicentre study for clinical, biomarker, and genetic studies. Radiological pattern recognition was examined by hierarchical clustering analysis. RESULTS: We identified 22 genetic conditions in 30 out of 62 paediatric patients (37 males, 25 females; mean age at onset 2y, SD 3; range 0-10y; mean age at assessment 11y, range 1-25y) through gene panels (n=11), whole-exome sequencing (n=13), and mitochondrial DNA (mtDNA) sequencing (n=6). Genetic aetiologies included mitochondrial diseases (57%), Aicardi-Goutières syndrome (20%), and monogenic causes of dystonia and/or epilepsy (17%) mimicking Leigh syndrome. Radiological abnormalities included T2-hyperintense lesions (n=26) and lesions caused by calcium or manganese mineralization (n=9). Three clusters were identified: the pallidal, neostriatal, and striatal, plus the last including mtDNA defects in the oxidative phosphorylation system with prominent brain atrophy. Mitochondrial biomarkers showed poor sensitivity and specificity in children with mitochondrial disease, whereas interferon signature was observed in all patients with patients with Aicardi-Goutières syndrome. INTERPRETATION: Combined whole-exome and mtDNA sequencing allowed the identification of several genetic conditions affecting basal ganglia metabolism. We propose a diagnostic algorithm which prioritizes early use of next-generation sequencing on the basis of three clusters of basal ganglia lesions.
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Enfermedades de los Ganglios Basales , Enfermedades Mitocondriales , Enfermedades Autoinmunes del Sistema Nervioso , Enfermedades de los Ganglios Basales/diagnóstico , Enfermedades de los Ganglios Basales/genética , Niño , Preescolar , ADN Mitocondrial , Femenino , Humanos , Lactante , Recién Nacido , Imagen por Resonancia Magnética , Masculino , Enfermedades Mitocondriales/diagnóstico , Enfermedades Mitocondriales/genética , Mutación , Malformaciones del Sistema Nervioso , Estudios ProspectivosRESUMEN
BACKGROUND: A proportion of de novo variants in patients affected by genetic disorders, particularly those with autosomal dominant (AD) inheritance, could be the consequence of somatic mosaicism in one of the progenitors. There is growing evidence that germline and somatic mosaicism are more common and play a greater role in genetic disorders than previously acknowledged. In Marfan syndrome (MFS), caused by pathogenic variants in the fibrillin-1 gene (FBN1) gene, approximately 25% of the disease-causing variants are reported as de novo. Only a few cases of parental mosaicism have been reported in MFS. METHODS: Employing an amplicon-based deep sequencing (ADS) method, we carried out a systematic analysis of 60 parents of 30 FBN1 positive, consecutive patients with MFS with an apparently de novo pathogenic variant. RESULTS: Out of the 60 parents studied (30 families), the majority (n=51, 85%) had a systemic score of 0, seven had a score of 1 and two a score of 2, all due to minor criteria common in the normal population. We detected two families with somatic mosaicism in one of the progenitors, with a rate of 6.6% (2/30) of apparently de novo cases. CONCLUSIONS: The search for parental somatic mosaicism should be routinely implemented in de novo cases of MFS, to offer appropriate genetic and reproductive counselling as well as to reveal masked, isolated clinical signs of MFS in progenitors that may require specific follow-up.