Rare Disorder Research Articles

PSMD11 loss-of-function variants correlate with a neurobehavioral phenotype, obesity, and increased interferon response

Primary proteasomopathies have recently emerged as a new class of rare early-onset neurodevelopmental disorders (NDDs) caused by pathogenic variants in the PSMB1, PSMC1, PSMC3, or PSMD12 proteasome genes. Proteasomes are large multi-subunit protein complexes that maintain cellular protein homeostasis by clearing ubiquitin-tagged damaged, misfolded, or unnecessary proteins. In this study, we have identified PSMD11 as an additional proteasome gene in which pathogenic variation is associated with an NDD-causing proteasomopathy. PSMD11 loss-of-function variants caused early-onset syndromic intellectual disability and neurodevelopmental delay with recurrent obesity in 10 unrelated children. Our findings demonstrate that the cognitive impairment observed in these individuals could be recapitulated in Drosophila melanogaster with depletion of the PMSD11 ortholog Rpn6, which compromised reversal learning. Our investigations in subject samples further revealed that PSMD11 loss of function resulted in impaired 26S proteasome assembly and the acquisition of a persistent type I interferon (IFN) gene signature, mediated by the integrated stress response (ISR) protein kinase R (PKR). In summary, these data identify PSMD11 as an additional member of the growing family of genes associated with neurodevelopmental proteasomopathies and provide insights into proteasomal biology in human health.

A comprehensive review of iPS cell line-based disease modelling of the polyglutamine spinocerebellar ataxias 2 and 3: a focus on the research outcomes

Spinocerebellar ataxias (SCAs) are a rare autosomal dominant neurodegenerative disorder. To date, approximately 50 different subtypes of SCAs have been characterized. The prevalent types of SCAs are usually of PolyQ origin, wherein the disease pathology is a consequence of multiple glutamine residues being encoded onto the disease proteins, causing expansions. SCAs 2 and 3 are the most frequently diagnosed subtypes, wherein affected patients exhibit certain characteristic physiological manifestations, such as gait ataxia and dysarthria. Nevertheless, other clinical signs were exclusive to these subtypes. Recently, multiple molecular diagnostic methods have been developed to identify and characterize these subtypes. Despite these advancements, the molecular pathology of SCAs remains unknown. To further understand the mechanisms involved in neurodegenerative SCAs 2 and 3, patient-derived induced pluripotent stem cell (iPSC)-based modelling is a compelling avenue to pursue. We cover the present state of iPSC-based in-vitro illness modelling of SCA subtypes 2 and 3 below, along with a list of cell lines created, and the relevance of research outcomes to personalized autologous therapy.

TANGO2 deficiency disease is predominantly caused by a lipid imbalance.

TANGO2 deficiency disease (TDD) is a rare genetic disorder estimated to affect ∼8000 individuals worldwide. It causes neurodegeneration often accompanied by potentially lethal metabolic crises that are triggered by diet or illness. Recent work has demonstrated distinct lipid imbalances in multiple model systems either depleted for or devoid of the TANGO2 protein, including human cells, fruit flies and zebrafish. Importantly, vitamin B5 supplementation has been shown to rescue TANGO2 deficiency-associated defects in flies and human cells. The notion that vitamin B5 is needed for synthesis of the lipid precursor coenzyme A (CoA) corroborates the hypothesis that key aspects of TDD pathology may be caused by lipid imbalance. A natural history study of 73 individuals with TDD reported that either multivitamin or vitamin B complex supplementation prevented the metabolic crises, suggesting this as a potentially life-saving treatment. Although recently published work supports this notion, much remains unknown about TANGO2 function, the pathological mechanism of TDD and the possible downsides of sustained vitamin supplementation in children and young adults. In this Perspective, we discuss these recent findings and highlight areas for immediate scientific attention.

Clinical outcomes, demographics and associative analysis of lung cancer patients with Lambert-Eaton myasthenic syndrome: Insights from the National Inpatient Sample (NIS) database.

e20134 Background: Lambert-Eaton myasthenic syndrome (LEMS) is a rare neuromuscular junction disorder that may present as a paraneoplastic syndrome or a primary autoimmune disorder. Approximately 60% of LEMS patients have an underlying tumor, with the paraneoplastic form predominantly associated with small cell lung cancer (SCLC). Understanding the clinical outcomes and risks associated in lung cancer patients with LEMS is crucial in effective management of such patients. Methods: This retrospective study utilized inpatient hospitalization data from the National Inpatient Sample (NIS) between January 1, 2016, and December 31, 2019. Data of patients with a primary or secondary discharge diagnosis of lung cancer (ICD10-CM codes C34, C78.0, C46.5, D02.2) were obtained. Then, out of this population, we identified Lambert-Eaton myasthenic syndrome with ICD-10 codes (G70.80, G70.81, G73.1). The objective was to run a descriptive analysis of clinical outcomes, risks, demographics and associations of LEMS in patients with lung cancer. Results: A total of 204 cases of lung cancer hospitalizations with LEMS were analyzed. The mean age was 68.23 years, with a slight female (51.72%) preponderance as compared to male (48.28%). Race distribution revealed increased prevalence in White Caucasians (83%), followed by Black (7%), Hispanic (4.5%), Asian or Pacific Islander (3%), Native American (0.5%), and Other (2%). The majority were covered by Medicare (66.33%), followed by private insurance (26.13%). The mortality rate was 8.9%, with a mean length of stay of 10.35 days and mean hospital charges of $118,676. Clinical outcomes and risks were analyzed, with sepsis occurring in 17.6% of cases, pneumonia in 22.5%, and acute respiratory failure in 26.9%. Intubation/mechanical ventilation was necessary in 18.1% of cases. The incidence of urinary tract infection (UTI) was 16.7%, acute kidney injury (AKI) was 17.2%, and venous thromboembolism (VTE) was 6.4%. Additionally, interventions such as intravenous immunoglobulin (IVIG) therapy and blood transfusions were also noted. Conclusions: This study provides insights into the demographic characteristics and clinical outcomes of lung cancer patients with Lambert-Eaton myasthenic syndrome (LEMS). The findings highlight the need for comprehensive management strategies targeting associated complications like acute respiratory failure, intubation and need for mechanical ventilation, pneumonia, UTI, AKI, and VTE to improve patient outcomes, quality of care and effective patient education with regards to their diagnosis of LEMS in lung cancer.

Considerations for the development of iPSC-derived cell therapies: a review of key challenges by the JSRM-ISCT iPSC Committee

Since their first production in 2007, human induced pluripotent stem cells (iPSCs) have provided a novel platform for the development of various cell therapies targeting a spectrum of diseases, ranging from rare genetic eye disorders to cancer treatment. However, several challenges must be tackled for iPSC-based cell therapy to enter the market and achieve broader global adoption. This white paper, authored by the Japanese Society for Regenerative Medicine (JSRM) - International Society for Cell Therapy (ISCT) iPSC Committee delves into the hurdles encountered in the pursuit of safe and economically viable iPSC-based therapies, particularly from the standpoint of the cell therapy industry. It discusses differences in global guidelines and regulatory frameworks, outlines a series of quality control tests required to ensure the safety of the cell therapy, and provides details and important considerations around cost of goods (COGs), including the impact of automated advanced manufacturing.

Unmasking Sturge–Weber syndrome in adulthood: a case with extrafacial port-wine stain and delayed neurological symptoms

Background: Sturge–Weber syndrome (SWS) is a rare neurocutaneous disorder characterized by a facial port-wine birthmark, leptomeningeal angiomatosis, and glaucoma. This case report highlights the challenges of diagnosing SWS when presenting with atypical features. Here, the authors present a 55-year-old man with an extrafacial port-wine stain and delayed-onset seizures, deviating from the classic triad. Case presentation: A 55-year-old man presented with a recent seizure and a characteristic port-wine birthmark extending beyond the typical facial region. Neurological examination revealed no weakness, speech difficulties, or coordination problems. Ophthalmological examination didn’t reveal glaucoma. Limited resources restricted access to advanced imaging like MRI scans. However, based on the constellation of clinical findings, including the facial birthmark with angiomatosis and the new-onset seizure, the patient received a diagnosis of SWS. Treatment with Levetiracetam was initiated to prevent future seizures, and patient education on managing diabetes and hypertension was provided. Clinical discussion: This case underscores the importance of considering SWS in diagnosing adult-onset seizures, especially with a characteristic facial birthmark. The delayed presentation and isolated seizure suggest potentially less severe brain involvement. Resource limitations necessitated a clinical diagnosis and treatment with readily available medications. Conclusion: This case highlights the challenges of diagnosing atypical SWS presentations. Early diagnosis is crucial for prompt management and improved patient outcomes. Future research should focus on developing robust diagnostic tools and exploring novel treatment options for atypical SWS presentations.

Clinical and molecular characteristics of Korean patients with Kabuki syndrome.

Kabuki syndrome (KS) is a rare disorder characterized by typical facial features, skeletal anomalies, fetal fingertip pad persistence, postnatal growth retardation, and intellectual disabilities. Heterozygous variants of the KMT2D and KDM6A genes are major genetic causes of KS. This study aimed to report the clinical and genetic characteristics of KS. This study included 28 Korean patients (14 boys and 14 girls) with KS through molecular genetic testing, including direct Sanger sequencing, whole-exome sequencing, or whole-genome sequencing. The median age at clinical diagnosis was 18.5 months (IQR 7-58 months), and the median follow-up duration was 80.5 months (IQR 48-112 months). Molecular genetic testing identified different pathogenic variants of the KMT2D (n = 23) and KDM6A (n = 3) genes, including 15 novel variants. Patients showed typical facial features (100%), such as long palpebral fissure and eversion of the lower eyelid; intellectual disability/developmental delay (96%); short stature (79%); and congenital cardiac anomalies (75%). Although 71% experienced failure to thrive in infancy, 54% of patients showed a tendency toward overweight/obesity in early childhood. Patients with KDM6A variants demonstrated severe genotype-phenotype correlation. This study enhances the understanding of the clinical and genetic characteristics of KS.

AN UNCOMMON COMPLICATION OF EPIDERMODYSPLASIA VERRUCIFORMIS

Epidermodysplasia verruciformis (EV) is a rare autosomal recessive genetic disorder. which patients have a reduced immunological ability to defend against and eliminate certain types of human papillomavirus (HPV), resulting in persistent infection and an increased lifetime risk of developing cutaneous dysplasia and malignancy. mostly squamous cell carcinoma was seen on sunlight-exposed areas, especially on the extremities, and forehead. Malignant transformation began in the form of actinic keratosis and early micro- invasive squamous cell carcinoma of Bowens type, rarely basal cell carcinoma. We report the case of a young patient with a history of EV who presented with a basal cell carcinoma that developed over a short period of time. The patient was successfully treated surgically.

Imbalance between hippocampal projection cell and parvalbumin interneuron architecture increases epileptic susceptibility in mouse model of methyl CpG binding protein 2 duplication syndrome.

Methyl CpG-binding protein 2 (MECP2) duplication syndrome is a rare X-linked genomic disorder affecting predominantly males, which is usually manifested as epilepsy and autism spectrum disorder (ASD) comorbidity. The transgenic line MeCP2Tg1 was used for mimicking MECP2 duplication syndrome and showed autism-epilepsy co-occurrence. Previous works suggested that the excitatory/inhibitory (E/I) imbalance is a potential common mechanism for both epilepsy and ASD. The projection neurons and parvalbumin (PV) interneurons account for the majority of E/I balance in the hippocampus. Therefore, we explored how structural changes of projection and PV+ neurons occur in the hippocampus of MeCP2Tg1 mice and whether these morphological changes contribute to epilepsy susceptibility. We used the interneuron Designer receptors exclusively activated by designer drugs mouse model to inhibit inhibitory neurons in the hippocampus to verify the epilepsy susceptibility of MeCP2Tg1 (FVB, an inbred strain named as sensitivity to Friend leukemia virus) mice. Electroencephalograms were recorded for the definition of seizure. We performed retro-orbital injection of virus in MeCP2Tg1 (FVB):CaMKIIα-Cre (C57BL/6) mice or MeCP2Tg1:PV-Cre (C57BL/6) mice and their littermate controls to specifically label projection and PV+ neurons for structural analysis. Epilepsy susceptibility was increased in MeCP2Tg1 mice. There was a reduced number of PV neurons and reduced dendritic complexity in the hippocampus of MeCP2Tg1 mice. The dendritic complexity in MeCP2Tg1 mice was increased compared to wild-type mice, and total dendritic spine density in dentate gyrus of MeCP2Tg1 mice was also increased. Total dendritic spine density was increased in CA1 of MeCP2Tg1 mice. Overexpression of MeCP2 may disrupt crucial signaling pathways, resulting in decreased dendritic complexity of PV interneurons and increased dendritic spine density of projection neurons. This reciprocal modulation of excitatory and inhibitory neuronal structures associated with MeCP2 implies its significance as a potential target in the development of epilepsy and offers a novel perspective on the co-occurrence of autism and epilepsy.

A zebrafish tufm mutant model for the COXPD4 syndrome of aberrant mitochondrial function

Mitochondrial dysfunction is a critical factor leading to a wide range of clinically heterogeneous and often severe disorders due to its central role in generating cellular energy. Mutations in the TUFM gene are known to cause combined oxidative phosphorylation deficiency 4 (COXPD4), a rare mitochondrial disorder characterized by a comprehensive quantitative deficiency in mitochondrial respiratory chain (MRC) complexes. The development of a reliable animal model for COXPD4 is crucial for elucidating the roles and mechanisms of TUFM in disease pathogenesis and benefiting its medical management. In this study, we construct a zebrafish tufm−/− mutant that closely resembles the COXPD4 syndrome, exhibiting compromised mitochondrial protein translation, dysfunctional mitochondria with oxidative phosphorylation (OXPHOS) defects, and significant metabolic suppression of the tricarboxylic acid (TCA) cycle. Leveraging this COXPD4 zebrafish model, we comprehensively validate the clinical relevance of TUFM mutations and identify probucol as a promising therapeutic approach for managing COXPD4. Our data offer valuable insights for understanding mitochondrial diseases and developing effective treatments.

Hypertrophy of the inferior olivary nucleus in corticobasal degeneration: A neuropathological study.

Corticobasal degeneration (CBD) is a rare neurodegenerative disorder. The status of the inferior olivary nucleus (ION) in CBD has been inadequately investigated. In this study, we conducted a pathological investigation of the ION in CBD. We reviewed the data of Japanese patients with pathologically confirmed CBD who underwent consecutive autopsies between 1985 and 2020 at our institute. We retrospectively examined clinical data from medical records and clinicopathological conferences and semi-quantitatively assessed the ION, central tegmental tract, superior cerebellar peduncle, and dentate nucleus. Of the 32 patients included, 14 (43.8%) had hypertrophy of the ION (HION), of whom 6 showed laterality. In the 14 HION cases, with or without laterality, except in 1 unevaluable case, atrophy/myelin pallor of the central tegmental tract was observed on the same side as the hypertrophy. Ten patients with HION, with or without laterality, had atrophy/myelin pallor of the superior cerebellar peduncle on the contralateral side to the hypertrophy. The ION presents with hypertrophic changes in CBD. The lesion is a primary degeneration in CBD and is related to the degeneration of the Guillain-Mollaret triangle. This finding contributes to the elucidation of the specific pathological characteristics of CBD.

Endocrine Evaluation and Homeostatic Model Assessment in Patients with Cornelia de Lange Syndrome

The aim of this study was to expand knowledge about endocrine disorders in individuals with Cornelia de Lange syndrome (CdLS), a rare developmental genetic disorder with anomalies in multiple organs and systems. Hormone levels, clinical scores, anthropometric measurements, and molecular analysis were assessed in 24 individuals with CdLS. Hyperprolactinemia was the most common endocrine disorder. Three patients showed subclinical hypothyroidism. Concerning the gonadotropic axis, mildly delayed puberty was observed, as well as genital anomalies, such as cryptorchidism. Despite short stature, levels of insulin-like growth factor 1 and insulin-like growth factor-binding protein 3 tended to be normal. Three prepubertal individuals without risk factors had higher than normal values for the homeostatic model assessment of insulin resistance (HOMA-IR) and for insulinemia, suggesting insulin resistance. Furthermore, two adults had elevated body mass indexes associated with HOMA-IR values over the cut-off values. CdLS may lead to dysregulation of the endocrine system, particularly in patients with high HOMA-IR values and insulinemia who are at risk of insulin resistance. Therefore, clinical follow-up with comprehensive hormonal assessment appears warranted in individuals with CdLS.

Efficacy and Safety of Donidalorsen for Hereditary Angioedema

BackgroundHereditary angioedema is a rare disorder characterized by episodic, potentially life-threatening swelling caused by kallikrein–kinin dysregulation. Long-term prophylaxis can stabilize this system. Donidalorsen, an antisense oligonucleotide, specifically reduces prekallikrein expression.MethodsIn this phase 3, double-blind, randomized trial, we assigned patients with hereditary angioedema to receive donidalorsen (80 mg subcutaneously) or placebo once every 4 or 8 weeks. The primary end point was the time-normalized number of investigator-confirmed hereditary angioedema attacks per 4 weeks (attack rate) from week 1 to week 25.ResultsA total of 90 patients received donidalorsen every 4 weeks (45 patients), donidalorsen every 8 weeks (23 patients), or placebo (22 patients). The least-squares mean time-normalized attack rate was 0.44 (95% CI, 0.27 to 0.73) in the 4-week group, 1.02 (95% CI, 0.65 to 1.59) in the 8-week group, and 2.26 (95% CI, 1.66 to 3.09) in the placebo group. The mean attack rate from week 1 to week 25 was 81% lower (95% CI, 65 to 89) in the 4-week group than in the placebo group (P<0.001) and 55% lower (95% CI, 22 to 74) in the 8-week group than in the placebo group (P=0.004); the median reduction in the attack rate from baseline was 90% in the 4-week group, 83% in the 8-week group, and 16% in the placebo group. The mean attack rate during weeks 5 to 25 was 87% lower (95% CI, 72 to 94) in the 4-week group than in the placebo group (P<0.001) and 60% lower (95% CI, 25 to 79) in the 8-week group than in the placebo group. Donidalorsen administered every 4 weeks resulted in an improvement in the least-squares mean total score for the change at week 25 on the Angioedema Quality-of-Life Questionnaire (scores range from 0 to 100, with a score of 100 indicating the worst possible quality of life) that was 18.6 points (95% CI, 9.5 to 27.7) better than that with placebo (P<0.001). The most common adverse events were erythema at the injection site, headache, and nasopharyngitis; 98% of adverse events were mild or moderate in severity.ConclusionsDonidalorsen treatment reduced the hereditary angioedema attack rate, a finding that supports potential prophylactic use for hereditary angioedema. (Funded by Ionis Pharmaceuticals; OASIS-HAE ClinicalTrials.gov number, NCT05139810.)

Lung Diseases and Rare Disorders: Is It a Lysosomal Storage Disease? Differential Diagnosis, Pathogenetic Mechanisms and Management.

Pulmonologists may be involved in managing pulmonary diseases in children with complex clinical pictures without a diagnosis. Moreover, they are routinely involved in the multidisciplinary care of children with rare diseases, at baseline and during follow-up, for lung function monitoring. Lysosomal storage diseases (LSDs) are a group of genetic diseases characterised by a specific lysosomal enzyme deficiency. Despite varying pathogen and organ involvement, they are linked by the pathological accumulation of exceeding substrates, leading to cellular toxicity and subsequent organ damage. Less severe forms of LSDs can manifest during childhood or later in life, sometimes being underdiagnosed. Respiratory impairment may stem from different pathogenetic mechanisms, depending on substrate storage in bones, with skeletal deformity and restrictive pattern, in bronchi, with obstructive pattern, in lung interstitium, with altered alveolar gas exchange, and in muscles, with hypotonia. This narrative review aims to outline different pulmonary clinical findings and a diagnostic approach based on key elements for differential diagnosis in some treatable LSDs like Gaucher disease, Acid Sphingomyelinase deficiency, Pompe disease and Mucopolysaccharidosis. Alongside their respiratory clinical aspects, which might overlap, we will describe radiological findings, lung functional patterns and associated symptoms to guide pediatric pulmonologists in differential diagnosis. The second part of the paper will address follow-up and management specifics. Recent evidence suggests that new therapeutic strategies play a substantial role in preventing lung involvement in early-treated patients and enhancing lung function and radiological signs in others. Timely diagnosis, driven by clinical suspicion and diagnostic workup, can help in treating LSDs effectively.

Dopamine synthesis and transport: current and novel therapeutics for parkinsonisms.

Parkinsonism is the primary type of movement disorder in adults, encompassing a set of clinical symptoms, including rigidity, tremors, dystonia, bradykinesia, and postural instability. These symptoms are primarily caused by a deficiency in dopamine (DA), an essential neurotransmitter in the brain. Currently, the DA precursor levodopa (synthetic L-DOPA) is the standard medication to treat DA deficiency, but it only addresses symptoms rather than provides a cure. In this review, we provide an overview of disorders associated with DA dysregulation and deficiency, particularly Parkinson's disease and rare inherited disorders leading predominantly to dystonia and/or parkinsonism, even in childhood. Although levodopa is relatively effective for the management of motor dysfunctions, it is less effective for severe forms of parkinsonism and is also associated with side effects and a loss of efficacy over time. We present ongoing efforts to reinforce the effect of levodopa and to develop innovative therapies that target the underlying pathogenic mechanisms affecting DA synthesis and transport, increasing neurotransmission through disease-modifying approaches, such as cell-based therapies, nucleic acid- and protein-based biologics, and small molecules.

Posterior reversible encephalopathy syndrome with functional and motor sequelae: A case report

Posterior Reversible Encephalopathy Syndrome (PRES) is a rare clinicoradiological neurological disorder, initially elucidated in 1996, Since this first description of PRES numerous case reports and case series, as well as retrospective observational studies describing the syndrome have been published. Importantly, no randomized controlled studies have been performed, We present the case of a young patient with no significant medical history who presented with neurological symptoms consistent with Posterior Reversible Encephalopathy Syndrome (PRES). Brain MRI confirmed the diagnosis of Posterior Reversible Encephalopathy Syndrome (PRES). Additionally, the etiological assessment yielded negative results. A notable aspect in our patient's case is the persistence of sequelae, characterized by dexterity and grip impairment on the right side, hindering various activities of daily living. The diagnosis of PRES is both radiological and clinical, with MRI playing a crucial role. Treatment is primarily symptomatic, sometimes requiring intensive care unit admission. Prognosis is favorable in the majority of cases, but severe complications and even death can occur. The reversibility of initial symptoms is well-documented in the literature. Long-term functional impairment outcomes following PRES have not been adequately characterized in the literature. Therefore, it is necessary to conduct follow-up screenings in more patients presenting both typical and atypical PRES syndromes. This will provide insight into whether the functional and motor sequelae of PRES are less reversible.

Adult niemann-pick disease: A case report

Adult niemann-pick disease: A case report

Surgical management of a rare giant sacral meningocele in a child

IntroductionAnterior sacral meningocele is a rare congenital disorder, occurring isolated or in syndromic disease. Case reportA 15-year-old patient who complained of abdominal pain and urinary dysfunction was managed surgically. Imaging diagnosed a giant presacral meningocele and agenesis of the coccyx. DiscussionThe presentation of sacral meningocele can be poorly symptomatic, which is why some patients are diagnosed late. Sometimes, diagnosis is suggested by non-specific abdominal symptoms or complications. Abdominal-pelvic radiological examination and lumbar spine MRI are essential, and treatment must be surgical. There are several surgical approaches, but currently no consensus. ConclusionAn unusual huge presacral cystic mass in a young patient may be isolated or part of a syndrome, and can be asymptomatic for a long time, leading to late diagnosis. The surgical approach should be based on multidisciplinary discussion. We operated on a giant anterior sacral meningocele in a child using a posterior approach, with a satisfactory result.

Neurophenotype and genetic analysis of children with Aicardi‐Goutières syndrome in China

ABSTRACTImportanceAicardi–Goutières syndrome (AGS) is a rare genetic disorder mainly affecting the central nervous system and autoimmunity. However, research on AGS among Chinese patients is limited.ObjectiveTo summarize the neurologic phenotypes and genetic causes in pediatric AGS patients, providing insights for early recognition and diagnosis in the Chinese population.MethodsClinical features and neuroimaging results of the patients diagnosed with AGS from Beijing Children's Hospital between January 2018 and January 2022 were collected. Whole exome sequencing was used for genetic analysis.ResultsA total of 15 patients was included, all presenting with various neurological symptoms, including developmental delay (100%), motor skill impairment (100%), language disability (78.6%), dystonia (93.3%), microcephaly (73.3%), sleep disorders (26.7%), regression (20.0%), vessel disease (6.7%), and epilepsy (6.7%). Neuroimaging revealed intracranial calcification (86.7%), cerebral atrophy (73.3%), and leukodystrophy (73.3%). Seven genes were identified, with TREX1 being the most common (40.0%, 6/15), followed by IFIH1 (20.0%, 3/15). Variant c.294dupA (p.C99Mfs*3) was detected in four unrelated patients, accounting for 66.7% (4/6) patients with the TREX1 variant. A literature review showed that TREX1 gene mutations in 35.6% (21/59) of AGS patients among the Chinese population.InterpretationNeurological symptoms are the most prevalent and severe presentation of AGS. Diagnosis may be considered when symptoms such as developmental delay, dystonia, microcephaly, brain calcification, and leukodystrophy emerge. TREX1 mutations are predominant in the Chinese population.

Treatability of the KMT2-Associated Neurodevelopmental Disorders Using Antisense Oligonucleotide-Based Treatments

Neurodevelopmental disorders (NDDs) of genetic origin are a group of early-onset neurological diseases with highly heterogeneous etiology and a symptomatic spectrum that includes intellectual disability, autism spectrum disorder, and learning and language disorders. One group of rare NDDs is associated with dysregulation of the KMT2 protein family. Members of this family share a common methyl transferase function and are involved in the etiology of rare haploinsufficiency disorders. For each of the KMT2 genes, at least one distinct disorder has been reported, yet clinical manifestations often overlap for multiple of these individually very rare disorders. Clinical care is currently focused on the management of symptoms with no targeted treatments available, illustrating a high unmet medical need and the urgency of developing disease-modifying therapeutic strategies. Antisense oligonucleotides (ASOs) are one option to treat some of these rare genetic disorders. ASOs are RNA-based treatments that can be employed to modulate gene expression through various mechanisms. In this work, we discuss the phenotypic features across the KMT2-associated NDDs and which ASO approaches are most suited for the treatment of each associated disorder. We hereby address variant-specific strategies as well as options applicable to larger groups of patients.