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Patients with the Aicardi–Goutières syndrome, an autosomal recessive disorder that affects the central nervous system, immune system, and skin, have severe neurodevelopmental abnormalities and abnormal signaling in the interferon pathway. In patients in this study, Janus kinase inhibition decreased skin manifestations and improved neurologic function.

Background Leukodystrophies are a clinically and genetically heterogeneous group of diseases characterized by white matter abnormalities on brain magnetic resonance imaging. Clinical, biochemical, molecular, and/or neuroimaging findings collectively support the diagnosis confirmation. The heterogeneous and overlapping clinical presentations of different leukodystrophies and non-diagnostic molecular testing pose a significant challenge to establishing a definitive diagnosis in these rare diseases. The Myelin Disorders Biorepository Project is an observational research program that aims to establish new tests to diagnose leukodystrophies and describe the natural history of these disorders. Ensuring an accurate diagnosis is critical to the goals of this project, and this paper aims to describe the rigorous diagnostic review and confirmation process which was developed. Results We present a diagnosis review process that contributes to an accurate diagnosis for participants enrolled in this study. Board-certified genetic counselors with expertise in these disorders audit medical records to carefully assess each enrolled participant’s clinical, biochemical, and molecular features. A scale of diagnostic categories is assigned based on the record review, and a team of leukodystrophy physician experts consults for cases that require further characterization or clarification. Conclusions This robust review process has resulted in a database of individuals with verified diagnoses that may be easily queried for inclusion in appropriate natural history studies and/or treatment trials. This is a model framework that may be adapted and implemented by other rare disease groups.

Purpose Recent reports of individuals with cytoplasmic transfer RNA (tRNA) synthetase-related disorders have identified cases with phenotypic variability from the index presentations. We sought to assess phenotypic variability in individuals with AARS1- related disease. Methods A cross-sectional survey was performed on individuals with biallelic variants in AARS1 . Clinical data, neuroimaging, and genetic testing results were reviewed. Alanyl tRNA synthetase (AlaRS) activity was measured in available fibroblasts. Results We identified 11 affected individuals. Two phenotypic presentations emerged, one with early infantile–onset disease resembling the index cases of AARS1- related epileptic encephalopathy with deficient myelination ( n  = 7). The second ( n  = 4) was a later-onset disorder, where disease onset occurred after the first year of life and was characterized on neuroimaging by a progressive posterior predominant leukoencephalopathy evolving to include the frontal white matter. AlaRS activity was significantly reduced in five affected individuals with both early infantile–onset and late-onset phenotypes. Conclusion We suggest that variants in AARS1 result in a broader clinical spectrum than previously appreciated. The predominant form results in early infantile–onset disease with epileptic encephalopathy and deficient myelination. However, a subgroup of affected individuals manifests with late-onset disease and similarly rapid progressive clinical decline. Longitudinal imaging and clinical follow-up will be valuable in understanding factors affecting disease progression and outcome.

Importance Leukodystrophies are a diverse group of rare disorders that disrupt central myelination. These disorders present with a broad spectrum of neurological severity and are associated with a range of potential secondary complications, such as scoliosis and failure of independent feeding. Objective We explore real‐world data of leukodystrophy complications to inform future evidence‐based care guidelines across these rare diseases. Design In a cross‐sectional observational study, we use a leukodystrophy‐specific research consortium and the availability of electronic health records (EHR) to capture a cross‐section of real‐world data. Setting Study participants were identified using EHR data from five hospital systems with established expertise in leukodystrophies. Participants Principal investigators or genetic counselors confirmed leukodystrophy diagnoses in all participants. Exposures Time‐to‐event measures were collected, including orthopedic complications (scoliosis, hip subluxation/dislocation), loss of ambulation, artificial ventilation, gastrostomy tube placement, and urinary tract infections (UTIs). Maximum motor milestones, including gain of ambulation by 2 years of age, were captured to stratify cohorts by neurological severity. Main Outcome and Measure A primary outcome was not prespecified, as this was an observational study. Results In total, 1203 participants were identified across 42 leukodystrophies (age range of 9 days to 89 years at last encounter). The most common event was feeding tube placement, and the median time to any first complication varied between disorders (Fleming–Harrington weighted log‐rank test). The specific diagnosis correlated with maximum gross motor milestone attainment (chi‐square test of independence). When all disorders were stratified by maximum motor milestone attainment (not specific diagnosis), the median time to adverse events was significantly associated with function (Fleming–Harrington weighted log‐rank test). Conclusions This cross‐sectional, retrospective observational study demonstrated that key medical events could be identified across institutions using EHR capture. Rates of health events and attainment of maximum motor milestones varied by specific leukodystrophy type. However, when the overall cohort was stratified by severity of motor impairment rather than individual diagnoses, the frequency of health events was associated with motor function. Our findings suggest utility for development of comprehensive care models for leukodystrophies as stratified by motor function and demonstrate the utility of integrated EHR review for real‐world data analyses.

OBJECTIVES/SPECIFIC AIMS: Metachromatic leukodystrophy (MLD) is a rare, lysosomal storage disorder caused by decreased enzymatic activity of arylsulfatase A. This can be the result of mutations in the ASA gene, or in rare cases PSAP. Historically, MLD has been subdivided into 3 forms based on age of onset: late infantile, juvenile, and adult. These subtypes were defined decades ago, prior to the appreciation of the full clinical spectrum of this lysosomal storage disorder and the advent of genetic testing. As a consequence, these empiric age-based historical definitions do not fully account for the spectrum of disease and are not founded in evidence-based analysis of phenotypic cohorts. Additionally, the antiquated definitions do not fully predict presenting features or disease course, and they fail to stratify outcomes in the few therapies currently available to treat this disease. As novel targeted therapeutics are developed, it is essential to have a clear understanding of the clinical presentation and natural history of MLD. Without properly defined sub-populations, it is difficult to design a therapeutic clinical trial that can demonstrate efficacy in a heterogeneous group. METHODS/STUDY POPULATION: In this project, we collected the retrospective natural history of over 50 individuals from around the world. We created an electronic database in REDCap to able to longitudinally collect clinical information. Using this retrospective natural history approach to understanding the disease course of individuals affected by MLD, we were able to characterize age of onset, delay to diagnosis, and common presenting features. RESULTS/ANTICIPATED RESULTS: Our results suggest distinct clinical phenotypic subgroups, with distinct presentations. DISCUSSION/SIGNIFICANCE OF IMPACT: With a better understanding of the natural history of MLD, we will be able to better counsel families and to design clinical trials with more coherent cohorts and more appropriate clinical endpoints.

ObjectiveTo determine the potential disease association between variants in LMBRD2 and complex multisystem neurological and developmental delay phenotypes.MethodsHere we describe a series of de novo missense variants in LMBRD2 in 10 unrelated individuals with overlapping features. Exome sequencing or genome sequencing was performed on all individuals, and the cohort was assembled through GeneMatcher.Results LMBRD2 encodes an evolutionary ancient and widely expressed transmembrane protein with no known disease association, although two paralogues are involved in developmental and metabolic disorders. Exome or genome sequencing revealed rare de novo LMBRD2 missense variants in 10 individuals with developmental delay, intellectual disability, thin corpus callosum, microcephaly and seizures. We identified five unique variants and two recurrent variants, c.1448G>A (p.Arg483His) in three cases and c.367T>C (p.Trp123Arg) in two cases. All variants are absent from population allele frequency databases, and most are predicted to be deleterious by multiple in silico damage-prediction algorithms.ConclusionThese findings indicate that rare de novo variants in LMBRD2 can lead to a previously unrecognised early-onset neurodevelopmental disorder. Further investigation of individuals harbouring LMBRD2 variants may lead to a better understanding of the function of this ubiquitously expressed gene.

Alexander disease results from gain of function mutations in the gene encoding glial fibrillary acidic protein (GFAP), an intermediate filament protein expressed in astrocytes. At least eight GFAP isoforms have been described, however, the predominant alpha isoform accounts for approximately 90% of GFAP protein in the central nervous system. Here we describe exonic variants identified in three unrelated families with Type II Alexander disease that alter the splicing of GFAP pre-mRNA and result in upregulation of a previously uncharacterized GFAP lambda isoform (NM 001363846.1). Affected members of Family 1 and Family 2 shared the same missense variant, NM 001363846.1:c.1289G>A;p.(Arg430His) while in Family 3 we identified a synonymous variant in the adjacent nucleotide, NM 001363846.1:c.1290C>A;p.(Arg430Arg). Using RNA and protein analysis of brain autopsy samples, and a mini-gene splicing reporter assay, we demonstrate both variants result in upregulation of the lambda isoform. We assessed other GFAP variants in the ClinVar database for predicted aberrant splicing and using the same assay demonstrated significant changes to splicing for two selected variants. Our approach demonstrates the importance of characterizing the effect of GFAP variants on mRNA splicing in order to inform future pathophysiologic and therapeutic study for Alexander disease.