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L-2-hydroxyglutaric aciduria (L2HGA) is a rare autosomal recessive neurometabolic disorder caused by the deficiency of L-2-hydroxyglutarate dehydrogenase (L2HGDH) enzyme. Dystonia, ataxia, pyramidal involvement and seizures are the common clinical manifestations. Coexisting behavioural problems and intellectual disability are also seen, however attention deficit hyperactivity disorder (ADHD) as the presenting clinical feature in L2HGA is rarely described. Here, we report a 5-year-old boy with behavioural problems and mild language delay. On clinical assessment, he fulfilled the diagnostic criteria for ADHD. His MR brain sequences showed classical finding of L2HGA—bilateral symmetrical T2-weighted hyperintensity involving subcortical white matter, basal ganglia and dentate nucleus. Urine analysis showed increased levels of 2-hydroxyglutaric acid and exome sequencing (targeted leukodystrophy panel) revealed homozygous likely pathogenic mutation in L2HGDH. He was started on high dose of riboflavin and levocarnitine and rehabilitative measures with which he had improvement in behavioural symptoms. This case illustrates the pivotol role of MR brain imaging in the diagnosis of inborn errors of metabolism.

Aicardi–Goutières syndrome (AGS) is a congenital inflammatory disorder accompanied by overactivated type I IFN signaling and encephalopathy with leukodystrophy and intracranial calcification. To date, none of the mouse models carrying an AGS-causative mutation has mimicked such brain pathology. Here, we established a mutant mouse model carrying a K948N point mutation, corresponding to an AGS-causative K999N mutation, located in a deaminase domain of the Adar1 gene that encodes an RNA editing enzyme. Adar1K948N/K948N mice displayed postnatal growth retardation. Hyperplasia of splenic white pulps with germinal centers and hepatic focal inflammation were observed from 2 mo of age. Inflammation developed in the lungs and heart with lymphocyte infiltration in an age-dependent manner. Furthermore, white matter abnormalities with astrocytosis and microgliosis were detected at 1 y of age. The increased expression of IFN-stimulated genes was detected in multiple organs, including the brain, from birth. In addition, single-nucleus RNA sequencing revealed that this elevated expression of IFN-stimulated genes was commonly observed in all neuronal subtypes, including neurons, oligodendrocytes, and astrocytes. We further showed that a K948N point mutation reduced the RNA editing activity of ADAR1 in vivo. The pathological abnormalities found in Adar1K948N/K948N mice were ameliorated by either the concurrent deletion of MDA5, a cytosolic sensor of unedited transcripts, or the sole expression of active ADAR1 p150, an isoform of ADAR1. Collectively, such data suggest that although the degree is mild, Adar1K948N/K948N mice mimic multiple AGS phenotypes, including encephalopathy, which is caused by reduced RNA editing activity of the ADAR1 p150 isoform.

Background The AARS2 gene encodes a mitochondrial alanyl-transfer RNA synthetase. Defects in this gene have been linked with autosomal recessive inheritance of a variety of different clinical phenotypes. Case A 13 year-old boy developed behavioral and psychiatric problems following a mild head injury. At age 21 he developed tremor, parkinsonism, and eye nystagmus. MRI revealed white matter changes consistent with a leukoencephalopathy. Genetic studies revealed two pathogenic mutations in the AARS2 gene (c.647dupG and c.595C > T). Literature review Only 47 cases of AARS2-associated disorders have been reported, with equal numbers of males and females, and age at onset ranging from infancy to 44 years. The most common clinical problems include movement disorders (71%), cognitive impairment (67%), corticospinal signs (64%), behavioral or psychiatric features (46%), and eye signs (34%). Imaging evidence suggestive of leukoencephalopathy is common, but not invariant. Premature ovarian failure is frequent in females, but not universal. Conclusions Defects in the AARS2 gene are a rare cause for a variety of movement disorders, often associated with brain imaging evidence suggestive of leukoencephalopathy.

Neurodegenerative diseases (NDD) are a heterogeneous group of disorders characterized by progressive loss of previously acquired skills that are of varied etiology, clinical manifestations, and natural course. There is a paucity of data on clinical profile of neurodegenerative diseases in our population. We conducted a retrospective study with 68 diagnosed cases of NDD at a tertiary care hospital in Bangladesh. Among them, more than one-third of children were in 1-5 years age group. The mean age was 10.2±3.1 year and male to female ratio was 2:1. Fifty percent of cases had a history of consanguineous parents. Leukodystrophy was most common (30.88%) among NDDs, followed by Wilson disease (26.47), SSPE (22.1%), and Degenerative Ataxia (20.59%). Motor skill regression was the most common presentation (97%), followed by speech regression in 91% and Gait disorder in 83% of children. Seizure was presenting features in 24% of children. Neuroimaging abnormalities were found in 80.88% NDD cases. Among them white matter hyper intensity in 29.41%, cerabeller atrophy in 13.25 %, and cerebral atropy in 11.76% of children. Eye changes were found in about two-thirds (69.12%) of cases of NDD. Among them, optic atrophy was found in 29.41%, and KF rings in 25.00% of cases.

Pathogenic biallelic variants in POL3RA have been associated with different disorders characterized by progressive neurological deterioration. These include the 4H leukodystrophy syndrome (hypomyelination, hypogonadotropic hypogonadism, and hypodontia) and adolescent-onset progressive spastic ataxia, as well as Wiedemann-Rautenstrauch syndrome (WRS), a recognizable neonatal progeroid syndrome. The phenotypic differences between these disorders are thought to occur mainly due to different functional effects of underlying POLR3A variants. Here we present the detailed clinical course of a 37-year-old woman in whom we identified a homozygous synonymous POLR3A variant c.3336G>A resulting in leaky splicing r.[3336ins192, =, 3243_3336del94]. She presented at birth with intrauterine growth retardation, lipodystrophy, muscular hypotonia, and several WRS-like facial features, albeit without sparse hair and prominent scalp veins. She had no signs of developmental delay or intellectual disability. Over the years, above characteristic facial features, she showed severe postnatal growth retardation, global lipodystrophy, joint contractures, thoracic hypoplasia, scoliosis, anodontia, spastic quadriplegia, bilateral hearing loss, aphonia, hypogonadotropic hypogonadism, and cerebellar peduncles hyperintensities in brain imaging. These manifestations partially overlap the clinical features of the previously reported POLR3A-associated disorders, mostly mimicking the WRS. Thus, our study expands the POLR3A-mediated phenotypic spectrum and suggests existence of a phenotypic continuum underlying biallelic POLR3A variants.

BACKGROUND: Krabbe disease, also called globoid cell leukodystrophy, is an autosomal recessive disease caused by a deficiency of lysosomal galactocerebrosidase. Infantile Krabbe occurring before 12 months of age accounts for most cases. Typical clinical features include irritability, seizures, peripheral neuropathy, and progressive neurodegeneration. METHODS: We collected and summarized the clinical and genetic data of an 8-month-old boy who demonstrated Krabbe disease onset at around 6 months. Potential pathogenic variants were screened by whole exome sequencing, and effects of candidate variants on alternative transcript and truncated protein were further validated at the RNA and protein level. RESULTS: Galactocerebrosidase activity was nearly absent in his blood, and whole exome sequencing revealed compound heterozygous variants [NM_000153.4: (c.658C>T); (c.328+5G>T)] in galactosylceramidase (GALC). The variant c.328+5G>T was predicted to alter splicing, and the abnormal isoform transcript was validated by observation of abnormal RNA isoforms. The variant c.658C>T was predicted to cause truncation of the protein, which was validated by western blotting. CONCLUSIONS: Our findings revealed compound heterozygous variants with solid experimental results for Krabbe disease and provides strong evidence for further Krabbe disease screening and clinical consulting. As a rare inherited systemic disorder, genetic variants in Krabbe disease should be investigated, as experimental validation for clinical diagnosis is needed.

Background Severe loss of TBCE function has been related to two well-known dysmorphic syndromes, while TBCE hypomorphic variants have been linked to neurodegenerative conditions due to perturbed microtubule dynamics and homeostasis, with signs of central and peripheral nervous system involvement. Method We report on an Italian female originating from Southern Italy who presented early-onset regression and neurodegeneration, with neurological features of tetraparesis and signs of peripheral nervous system involvement. Her brain MRI revealed white matter involvement. Results Analyzing all known hypomyelination leukodystrophies related genes, two mutations in TBCE (NM_001079515) were detected: the missense variant c.464 T > A; p. (Ile155Asn) and the frameshift variant c.924del; p. (Leu309Ter), in compound heterozygosity, already reported in the literature in patients coming from the same geographical area. The clinical phenotype of the proposita was more severe and with an earlier onset than the majority of the patients reported so far. Conclusions Next Generation Sequencing is becoming increasingly necessary to assess unusual phenotypes, with the opportunity to establish prognosis and disease mechanisms, and facilitating differential diagnosis.

Purpose: We present a case of retinal vasculopathy with cerebral leukodystrophy and review the usefulness of optical coherence tomography angiography (OCT-A) in the assessment of long-term outcomes. Case description: A 31-year-old woman developed sudden-onset scotoma in her right eye. Fundus examination and fluorescein angiography showed a patch of soft exudate and capillary nonperfusion in the posterior pole and outside the vascular arcades. OCT-A revealed that the initial vessel density (VD) of the superficial capillary plexus (SCP) and deep capillary plexus (DCP) of the right eye were 32% and 49.2%, respectively. Interestingly, over time, the VD of the SCP and DCP gradually decreased to 23.1% and 26.2%, respectively. In contrast, the initial VD of the SCP and DCP of the left eye were both stable at 44.3% and 56.2%, respectively, and only decreased slightly to 39.3% and 45.7%, respectively, over time. The average VD loss of the SCP and DCP, assessed over 1 year, was 8% and 13%, respectively, in the right eye, and 3% and 6%, respectively, in the left eye. Conclusion: Based on this case report, in which we demonstrated a long-term decline in VD of the macula in a young woman with mild retinal vasculopathy with cerebral leukodystrophy, we suggest that there is a potential and valuable role for OCT-A in this rare disease.

Polymeric nanoparticles are being extensively investigated as an approach for brain delivery of drugs, especially for their controlled release and targeting capacity. Nose-to-brain administration of nanoparticles, bypassing the blood brain barrier, offers a promising strategy to deliver drugs to the central nervous system. Here, we investigated the potential of hybrid nanoparticles as a therapeutic approach for demyelinating diseases, more specifically for Krabbe’s disease. This rare leukodystrophy is characterized by the lack of enzyme galactosylceramidase, leading to the accumulation of toxic psychosine in glial cells causing neuroinflammation, extensive demyelination and death. We present evidence that lecithin/chitosan nanoparticles prevent damage associated with psychosine by sequestering the neurotoxic sphingolipid via physicochemical hydrophobic interactions. We showed how nanoparticles prevented the cytotoxicity caused by psychosine in cultured human astrocytes in vitro, and how the nanoparticle size and PDI augmented while the electrostatic charges of the surface decreased, suggesting a direct interaction between psychosine and the nanoparticles. Moreover, we studied the effects of nanoparticles ex vivo using mouse cerebellar organotypic cultures, observing that nanoparticles prevented the demyelination and axonal damage caused by psychosine, as well as a moderate prevention of the astrocytic death. Taken together, these results suggest that lecithin-chitosan nanoparticles are a potential novel delivery system for drugs for certain demyelinating conditions such as Krabbe’s disease, due to their dual effect: not only are they an efficient platform for drug delivery, but they exert a protective effect themselves in tampering the levels of psychosine accumulation. Supplementary Information The online version contains supplementary material available at 10.1007/s13311-021-01109-3.

Colony-stimulating factor 1 receptor (CSF1R)-related leukoencephalopathy is one of the most common causes of adult-onset leukodystrophy and is caused by mutation of the CSF1R gene. Brain magnetic resonance imaging (MRI) findings in asymptomatic patients have not been well recognized. We report on the case of a patient with CSF1R-related leukoencephalopathy who had a novel missense variant of the CSF1R gene with a family history of early onset dementia. This is a representative case of CSF1R-related leukoencephalopathy, which shows the progression of brain MRI and cognitive decline from an asymptomatic state.

Vanishing white matter disease (VWMD) due to eIF2B mutations is a common leukodystrophy characterised by childhood onset, autosomal recessive inheritance, and progressive clinical course with episodic worsening. There are no reports of genetically confirmed adult patients from India. We describe the phenotype of two adults with genetically confirmed VWMD and typical radiological findings. Both had spastic ataxia and cognitive and behavioural disturbances. Other neurological features included myoclonic jerks and parkinsonism. At the last follow-up (duration: 2–9 years), one patient was wheelchair-bound. VWMD is rare in adults but should be suspected based on radiological findings and confirmed by eIF2B mutation.

KARS encodes lysyl-tRNA synthetase, which is essential for protein translation. KARS mutations sometimes cause impairment of cytoplasmic and mitochondrial protein synthesis, and sometimes lead to progressive leukodystrophies with mitochondrial signature and psychomotor regression, and follow a rapid regressive course to premature death. There has been no disease-modifying therapy beyond supportive treatment. We present a 5-year-old male patient with an asymmetrical leukodystrophy who showed overt evidence of mitochondrial dysfunction, including elevation of lactate on brain MR spectroscopy and low oxygen consumption rate in fibroblasts. We diagnosed this patient's condition as KARS-related leukodystrophy with cerebral calcification, congenital deafness, and evidence of mitochondrial dysfunction. We employed a ketogenic diet as well as multiple vitamin supplementation with the intention to alleviate mitochondrial dysfunction. The patient showed alleviation of his psychomotor regression and even partial restoration of his abilities within 4 months. This is an early report of a potential disease-modifying therapy for KARS-related progressive leukodystrophy without appreciable adverse effects.

Mitochondrial dysfunction may activate innate immunity, e.g. upon abnormal handling of mitochondrial DNA in TFAM mutants or in altered mitophagy. Recent reports showed that also deletion of mitochondrial matrix peptidase ClpP in mice triggers transcriptional upregulation of inflammatory factors. Here, we studied ClpP-null mouse brain at two ages and mouse embryonal fibroblasts, to identify which signaling pathways are responsible, employing mass spectrometry, subcellular fractionation, immunoblots, and reverse transcriptase polymerase chain reaction. Several mitochondrial unfolded protein response factors showed accumulation and altered migration in blue-native gels, prominently the co-chaperone DNAJA3. Its mitochondrial dysregulation increased also its extra-mitochondrial abundance in the nucleus, a relevant observation given that DNAJA3 modulates innate immunity. Similar observations were made for STAT1, a putative DNAJA3 interactor. Elevated expression was observed not only for the transcription factorsStat1/2, but also for two interferon-stimulated genes (Ifi44,Gbp3). Inflammatory responses were strongest for the RLR pattern recognition receptors (Ddx58,Ifih1,Oasl2,Trim25) and several cytosolic nucleic acid sensors (Ifit1,Ifit3,Oas1b,Ifi204,Mnda). The consistent dysregulation of these factors from an early age might influence also human Perrault syndrome, where ClpP loss-of-function leads to early infertility and deafness, with subsequent widespread neurodegeneration.

Krabbe disease, an inherited leukodystrophy, is a sphingolipidosis caused by deficiency of β-galactocerebrosidase: it is characterized by myelin loss, and pathological activation of macrophage/microglia and astrocytes. To define driving pathogenic factors, we explored the expression repertoire of candidate neuroinflammatory genes: upregulation of receptor interacting protein kinase 1 (Ripk1) and disease-associated microglia (DAM) genes, including Cst7 and Ch25h, correlated with severity of Krabbe disease genetically modelled in the twitcher mouse. Upregulation of Ripk1 in Iba1/Mac2-positive microglia/macrophage associated with the pathognomic hypertrophic/globoid phenotype of this disease. Widespread accumulation of ubiquitinin1 in white and grey matter co-localised with p62. In Sandhoff disease, another sphingolipid disorder, neuroinflammation, accumulation of p62 and increased Ripk1 expression was observed. The upregulated DAM genes and macrophage/microglia expression of Ripk1 in the authentic model of Krabbe disease strongly resemble those reported in Alzheimer disease associating with disturbed autophagosomal/lysosomal homeostasis. Activation of this shared molecular repertoire, suggests the potential for therapeutic interdiction at a common activation step, irrespective of proximal causation. To clarify the role of Ripk1 in the pathogenesis of Krabbe disease, we first explored the contribution of its kinase function, by intercrossing twitcher and the K45A kinase-dead Ripk1 mouse and breeding to homozygosity. Genetic ablation of Ripk1 kinase activity neither altered the neuropathological features nor the survival of twitcher mice. We conclude that Ripk1 kinase-dependent inflammatory and degenerative capabilities play no instrumental role in Krabbe disease; however, putative kinase-independent functions of Ripk1 remain formally to be explored in its molecular pathogenesis.

Megalencephalic Leukoencephalopathy with subcortical Cysts (MLC) is a type of vacuolating leukodystrophy, which is mainly caused by mutations in MLC1 or GLIALCAM. The two MLC-causing genes encode for membrane proteins of yet unknown function that have been linked to the regulation of different chloride channels such as the ClC-2 and VRAC. To gain insight into the role of MLC proteins, we have determined the brain GlialCAM interacting proteome. The proteome includes different transporters and ion channels known to be involved in the regulation of brain homeostasis, proteins related to adhesion or signaling as several G protein-coupled receptors (GPCRs), including the orphan GPRC5B and the proposed prosaposin receptor GPR37L1. Focusing on these two GPCRs, we could validate that they interact directly with MLC proteins. The inactivation of Gpr37l1 in mice upregulated MLC proteins without altering their localization. Conversely, a reduction of GPRC5B levels in primary astrocytes downregulated MLC proteins, leading to an impaired activation of ClC-2 and VRAC. The interaction between the GPCRs and MLC1 was dynamically regulated upon changes in the osmolarity or potassium concentration. We propose that GlialCAM and MLC1 associate with different integral membrane proteins modulating their functions and acting as a recruitment site for various signaling components as the GPCRs identified here. We hypothesized that the GlialCAM/MLC1 complex is working as an adhesion molecule coupled to a tetraspanin-like molecule performing regulatory effects through direct binding or influencing signal transduction events.

Funder: National Multiple Sclerosis Society; Id: http://dx.doi.org/10.13039/100000890, Funder: Association Européenne contre les Leucodystrophies; Id: http://dx.doi.org/10.13039/501100008731, Funder: New York Stem Cell Foundation; Id: http://dx.doi.org/10.13039/100003194, Funder: University of California, San Francisco; Id: http://dx.doi.org/10.13039/100008069, Funder: Sandler Foundation; Id: http://dx.doi.org/10.13039/100007100, Funder: Action Medical Research; Id: http://dx.doi.org/10.13039/501100000317, Funder: Dr. Miriam and Sheldon G. Adelson Medical Research Foundation; Id: http://dx.doi.org/10.13039/100005984, Funder: National Institute for Health Research; Id: http://dx.doi.org/10.13039/501100000272, Funder: Stanford University; Id: http://dx.doi.org/10.13039/100005492, Funder: Foundation Optic Atrophy 1, Oligodendrocytes, the myelinating cells of the central nervous system, possess great potential for disease modeling and cell transplantation-based therapies for leukodystrophies. However, caveats to oligodendrocyte differentiation protocols ( Ehrlich et al., 2017; Wang et al., 2013; Douvaras and Fossati, 2015) from human embryonic stem and induced pluripotent stem cells (iPSCs), which include slow and inefficient differentiation, and tumorigenic potential of contaminating undifferentiated pluripotent cells, are major bottlenecks towards their translational utility. Here, we report the rapid generation of human oligodendrocytes by direct lineage conversion of human dermal fibroblasts (HDFs). We show that the combination of the four transcription factors OLIG2, SOX10, ASCL1 and NKX2.2 is sufficient to convert HDFs to induced oligodendrocyte precursor cells (iOPCs). iOPCs resemble human primary and iPSC-derived OPCs based on morphology and transcriptomic analysis. Importantly, iOPCs can differentiate into mature myelinating oligodendrocytes in vitro and in vivo. Finally, iOPCs derived from patients with Pelizaeus Merzbacher disease, a hypomyelinating leukodystrophy caused by mutations in the proteolipid protein 1 (PLP1) gene, showed increased cell death compared with iOPCs from healthy donors. Thus, human iOPCs generated by direct lineage conversion represent an attractive new source for human cell-based disease models and potentially myelinating cell grafts.

Болезнь Краббе (БКр) - редкое наследственное аутосомно-рецессивное заболевание, входящее в группу лизосомных болезней накопления. Заболевание обусловлено мутациями в гене GALC, приводящими к дефициту фермента галактозилцерамидазы. Частота БКр оценивается как 1:100 000 живых новорожденных, хотя в некоторых странах регистрируется более высокая частота заболевания. Точная частота БКр в Российской Федерации и в ее регионах неизвестна. Мажорной мутацией, приводящей к развитию БКр, является крупная делеция затрагивающая 11-17 экзоны гена GALC c.1161+6532_polyA+9kbdel (IVS10del30kb). Доля этой мутации в европейской популяции оценивается примерно в 50% от всех мутаций. Для изучения спектра и частот мутаций гена GALC на территории РФ были обследованы пациенты из разных регионов. Частая делеция составила 54% от общего числа выявленных мутаций, что сопоставимо с данными по европейской популяции. Однако в Чеченской Республике данная мутация встречалась гораздо чаще, чем в других регионах. Среди 950 исследованных образцов было выявлено 7 гетерозиготных носителей частой мутации. Учитывая вклад других мутаций, расчётная частота БКр в республике составила 1:51237, что превышает таковую в европейской популяции. Дополнительный анализ всех найденных мутаций гена GALC позволил выявить вариант c.578T>C, p.Ile193Thr, аллельная частота которого составила 8%. Данная замена впервые была описана у пациентов из нашей выборки и встречается только при поздней инфантильной форме заболевания у русских пациентов. Krabbe’s disease (KD) is a rare inherited autosomal recessive lysosomal storage disease. KD is caused by mutations in the GALC gene leading to deficiency of galactosylceramidase. KD oссurs in 1 per 100 000 newborns, although some countries have a higher incidence rate. The exact KD incidence in Russia is unknown. A major mutation leading to the KD development is a large deletion affecting exons 11-17 of the GALC gene с.1161+6532_polyA+9kbdel (IVS10del30kb). This mutation occurs in 50% of KD cases in the European population. Patients from different regions were studied to analyze the mutation spectrum and the incidence in the Russian population. The incidence rate of the large deletion in our study equals 54%, that is comparable with European population. However, in the Chechen Republic this mutation is much more common than in other regions. 950 samples were studied, 7 heterozygous carriers of frequent mutation were identified. Thus, the estimated KD incidence rate is 1:51237 considering other mutations, and it is higher than that in the European population. Additional analysis of all detected GALC mutations revealed a genetic variant c.578T>C, p.Ile193Thr with allelic frequency measured up 8%. This substitution was described in our selection for the first time and presented only in Russian patients with late infantile form of the disease.

X-linked adrenoleukodystrophy (ALD) is a leukodystrophy characterized not only by progressive loss of myelin in the central nervous system due to dysmyelination, but also by acute, subacute, or chronic inflammatory demyelination. This results in the phenotypic variability of cerebral ALD (cerALD), which is independent of the genotype. In this article, we reported a fulminant presentation with fluctuating encephalopathy and visual loss in a patient with childhood onset cerALD. Brain MRI showed symmetric confluent occipito-temporal demyelination with severe disruption of the blood–brain barrier and prechiasmal optic neuropathy. The patient's cerebral spinal fluid (CSF) demonstrated an elevated IgG index, myelin basic proteins, and oligoclonal bands. Within 48 hours of receiving immunomodulating therapy, the patient's symptoms of psychomotor slowing, visual impairment, and areflexia partially resolved. High plasma C26:0 levels and high ratios of C24/22 and C26/22 were diagnostic of ALD. It has been shown that environmental factors play an important role in the inflammatory demyelination responsible for the severe phenotypes of cerALD.

Cerebral folate transporter deficiency syndrome, caused by FOLR-1 mutations is characterized by late infantile onset, severe developmental regression, epilepsy, and leukodystrophy. An extremely low concentration of 5-methyltetrahydrofolate in the cerebrospinal fluid provides a crucial clue to its diagnosis and is a treatment target. Oral or intravenous folinic acid (5-formyltetrahydrofolate) administration improves clinical symptoms and brain magnetic resonance imaging (MRI) findings. We describe three siblings carrying a novel homozygous FOLR1 nonsense mutation, that were referred due to intractable epilepsy and progressive neurological decline. Brain MRI showed hypomyelination and cerebellar atrophy. Folinic acid (oral and intravenous) supplementation, initiated after over 15 years illness, has failed to result in any sizeable clinical or neurophysiological improvement. Cerebral folate transport deficiency bears overlapping clinical features with many severe developmental encephalopathies. It is crucial to recognize FOLR1 signs and establish an early clinical and molecular diagnosis in order to provide timely folinic acid treatment and improve outcome.

X-linked adrenoleukodystrophy (X-ALD) is the most common leukodystrophy. Despite intensive research in recent years, it remains unclear, what drives the different clinical disease courses. Due to this missing pathophysiological link, therapy for the childhood cerebral disease course of X-ALD (CCALD) remains symptomatic; the allogenic hematopoietic stem cell transplantation or hematopoietic stem-cell gene therapy is an option for early disease stages. The inclusion of dried blood spot (DBS) C26:0-lysophosphatidylcholine to newborn screening in an increasing number of countries is leading to an increasing number of X-ALD patients diagnosed at risk for CCALD. Current follow-up in asymptomatic boys with X-ALD requires repetitive cerebral MRIs under sedation. A reliable and easily accessible biomarker that predicts CCALD would therefore be of great value. Here we report the application of targeted metabolomics by AbsoluteIDQ® p180-Kit from Biocrates to search for suitable biomarkers in X-ALD. LysoPC a C20:3 and lysoPC a C20:4 were identified as metabolites that indicate neuroinflammation after induction of experimental autoimmune encephalitis in the serum of Abcd1tm1Kds mice. Analysis of serum from X-ALD patients also revealed different concentrations of these lipids at different disease stages. Further studies in a larger cohort of X-ALD patient sera are needed to proof the diagnostic value of these lipids for use as early biomarkers for neuroinflammation in CCALD patients.

Globoid cell leukodystrophy (GLD), also known as Krabbe disease, is a lysosomal storage disorder causing extensive demyelination in the central and peripheral nervous systems. GLD is caused by loss-of-function mutations in the lysosomal hydrolase, galactosylceramidase (GALC), which catabolizes the myelin sphingolipid galactosylceramide. The pathophysiology of GLD is complex and reflects the expression of GALC in a number of glial and neural cell types in both the central and peripheral nervous systems (CNS and PNS), as well as leukocytes and kidney in the periphery. Over the years, GLD has garnered a wide range of scientific and medical interests, especially as a model system to study gene therapy and novel preclinical therapeutic approaches to treat the spontaneous murine model for GLD. Here, we review recent findings in the field of Krabbe disease, with particular emphasis on novel aspects of GALC physiology, GLD pathophysiology, and therapeutic strategies.

Summary Limited access to human oligodendrocytes impairs better understanding of oligodendrocyte pathology in myelin diseases. Here, we describe a method to robustly convert human fibroblasts directly into oligodendrocyte-like cells (dc-hiOLs), which allows evaluation of remyelination-promoting compounds and disease modeling. Ectopic expression of SOX10, OLIG2, and NKX6.2 in human fibroblasts results in rapid generation of O4+ cells, which further differentiate into MBP+ mature oligodendrocyte-like cells within 16 days. dc-hiOLs undergo chromatin remodeling to express oligodendrocyte markers, ensheath axons, and nanofibers in vitro, respond to promyelination compound treatment, and recapitulate in vitro oligodendroglial pathologies associated with Pelizaeus-Merzbacher leukodystrophy related to PLP1 mutations. Furthermore, DNA methylome analysis provides evidence that the CpG methylation pattern significantly differs between dc-hiOLs derived from fibroblasts of young and old donors, indicating the maintenance of the source cells’ “age.” In summary, dc-hiOLs represent a reproducible technology that could contribute to personalized medicine in the field of myelin diseases., Graphical abstract, Highlights • SOX10, OLIG2, and NKX6.2 directly convert human fibroblasts into dc-hiOLs in 16 days • dc-hiOLs express key oligodendrocyte markers • dc-hiOLs preserve the epigenetic age of donor cells • dc-hiOLs from PMD patients show maturation deficit and vulnerability to cell death, In this article, Kuhlmann and colleagues show that human fibroblasts can be directly converted into oligodendrocyte-like cells (dc-hiOLs) upon overexpression of SOX10, OLIG2, and NKX6.2. dc-hiOLs undergo chromatin remodeling to activate oligodendrocyte-related genes, perform ensheathment in vitro, and maintain the epigenetic age of donor cells. The applicability of dc-hiOLs in promyelination compound screening and disease-modeling studies is demonstrated.

Canavan disease is an autosomal recessive leukodystrophy caused by mutations in the gene encoding aspartoacylase (ASPA), which hydrolyses N-acetylaspartate (NAA) to acetate and aspartate. A similar feline neurodegenerative disease associated with a mutation in the ASPA gene is reported herein. Comprehensive clinical, genetic, and pathological analyses were performed on 4 affected cats. Gait disturbance and head tremors initially appeared at 1 to 19 months of age. These cats eventually exhibited dysstasia and seizures and died at 7 to 53 months of age. Magnetic resonance imaging of the brain revealed diffuse symmetrical intensity change of the cerebral cortex, brainstem, and cerebellum. Gas chromatography–mass spectrometry analysis of urine showed significant excretion of NAA. Genetic analysis of the 4 affected cats identified a missense mutation (c.859G>C) in exon 6 of the ASPA gene, which was not detected in 4 neurologically intact cats examined as controls. Postmortem analysis revealed vacuolar changes predominantly distributed in the gray matter of the cerebrum and brain stem as well as in the cerebellar Purkinje cell layer. Immunohistochemically, these vacuoles were surrounded by neurofilaments and sometimes contained MBP- and Olig2-positive cells. Ultrastructurally, a large number of intracytoplasmic vacuoles containing mitochondria and electron-dense granules were detected in the cerebral cortex. All 4 cats were diagnosed as spongy encephalopathy with a mutation in the ASPA gene, a syndrome analogous to human Canavan disease. The histopathological findings suggest that feline ASPA deficiency induces intracytoplasmic edema in neurons and oligodendrocytes, resulting in spongy degeneration of the central nervous system.

Aicardi-Goutieres Syndrome (AGS) is a monogenic leukodystrophy with pediatric onset, clinically characterized by a variable degree of neurologic impairment. It belongs to a group of condition called type I interferonopathies that are characterized by abnormal overproduction of interferon alpha, an inflammatory cytokine which action is mediated by the activation of two of the four human Janus Kinases. Thanks to an ever-increasing knowledge of the molecular basis and pathogenetic mechanisms of the disease, Janus Kinase inhibitors (JAKIs) have been proposed as a treatment option for selected interferonopathies. Here we reported the 24 months follow-up of the fifth AGS patient treated with ruxolitinib described so far in literature. The treatment was globally well tolerated; clinical examinations and radiological images demonstrated a progressively improving course. It is however to note that patients presenting with mild and spontaneously improving course have been reported. Large natural history studies on AGS spectrum are strongly required in order to get a better understanding of the results emerging from ongoing therapeutic trials on such rare disease.

Pelizaeus-Merzbacher-like disease (PMLD) is an autosomal recessive hypomyelinating leukodystrophy with clinical symptoms and imaging manifestations similar to those of Pelizaeus-Merzbacher disease (PMD), an X-linked recessive hypomyelinating leukodystrophy. Typical manifestations of PMLD are nystagmus, dysmyotonia, ataxia, progressive motor dysfunction, and diffuse leukodystrophy on magnetic resonance imaging (MRI). This report identified novel mutations in NCP1 causing PMLD. A 7-month-old male patient was referred to our hospital because he could not lift his head until that time. He had symptoms including congenital nystagmus, hypotonia, and developmental delay. According to the MRI scan, there were signs of leukodystrophy. According to the clinical manifestations and the results of whole-exome sequencing (compound heterozygote mutations in NPC1 (p. G911S, c2731G>A and p. D128H, c382G>C)), the diagnosis of PMLD was considered, and his parents were determined to be carriers of mutant genes. He began rehabilitation training at the age of 1 year old. After 5 years of training, he was still experiencing global developmental delay, equivalent to the developmental level of a nine-month-old child. PMLD is a disease that seriously affects the quality of life of children and can result from mutations in different genes. In this report, we expand the gene spectrum of PMLD and suggest early genetic counselling for suspected patients and their patients.

Purpose Metachromatic leukodystrophy (MLD) is a lysosomal storage disorder caused by the deficiency of arylsulfatase A (ARSA), which results in the accumulation of sulfatides. Newborn screening for MLD may be considered in the future as innovative treatments are advancing. We carried out a research study to assess the feasibility of screening MLD using dried blood spots (DBS) from de-identified newborns. Methods To minimize the false-positive rate, a two-tier screening algorithm was designed. The primary test was to quantify C16:0-sulfatide in DBS by ultraperformance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The screening cutoff was established based on the results from 15 MLD newborns to achieve 100% sensitivity. The secondary test was to measure the ARSA activity in DBS from newborns with abnormal C16:0-sulfatide levels. Only newborns that displayed both abnormal C16:0-sulfatide abundance and ARSA activity were considered screen positives. Results A total of 27,335 newborns were screened using this two-tier algorithm, and 2 high-risk cases were identified. ARSA gene sequencing identified these two high-risk subjects to be a MLD-affected patient and a heterozygote. Conclusion Our study demonstrates that newborn screening for MLD is highly feasible in a real-world scenario with near 100% assay specificity.

Peroxisomes play an essential role in lipid metabolism via interaction with other intracellular organelles. The information about the role of the Acyl-CoA-binding domain containing-protein 5 (ACBD5) in these interactions in human cells is emerging. Moreover, a few patients with retinal dystrophy and leukodystrophy caused by pathogenic variants in ACBD5 have been recently introduced. Here, we present a 36-year-old female with retinal dystrophy, leukodystrophy, and psychomotor regression due to a novel homozygous variant in ACBD5. Our study adds to the growing knowledge of this peroxisomal disorder by providing phenotypic details of the first adult patient.

Coats plus syndrome is an autosomal recessive multisystemic and pleiotropic disorder affecting the eyes, brain, bone, and gastrointestinal tract, usually caused by compound heterozygous variants of the conserved telomere maintenance component 1 gene (CTC1), involved in telomere homeostasis and replication. So far, most reported patients are compound heterozygous for a truncating mutation and a missense variant. The phenotype is believed to result from telomere dysfunction, with accumulation of DNA damage, cellular senescence, and stem cell depletion. Here, we report a 23-year-old female with prenatal and postnatal growth retardation, microcephaly, osteopenia, recurrent fractures, intracranial calcification, leukodystrophy, parenchymal brain cysts, bicuspid aortic valve, and primary ovarian failure. She carries a previously reported maternally inherited pathogenic variant in exon 5 (c.724_727del, p.(Lys242Leufs*41)) and a novel, paternally inherited splice site variant (c.1617+5G>T; p.(Lys480Asnfs*17)) in intron 9. CTC1 transcript analysis showed that the latter resulted in skipping of exon 9. A trace of transcripts was normally spliced resulting in the presence of a low level of wild-type CTC1 transcripts. We speculate that ovarian failure is caused by telomere shortening or chromosome cohesion failure in oocytes and granulosa cells, with early decrease in follicular reserve. This is the first patient carrying 2 truncating CTC1 variants and the first presenting primary ovarian failure.

Introduction Metachromatic leukodystrophy (MLD) refers to leukodystrophy caused by the accumulation of sulfatide from arylsulfatase A (ARSA) gene mutations. Sulfatide also accumulates in various organs, including the peripheral nerves, kidney, and gallbladder. Proliferative changes in the gallbladder have been reported in several patients, while gallbladder cancer is reported in only two adult MLD cases. We report what is likely the first pediatric case of MLD with gallbladder cancer. Case report The patient was a 5-year-old girl diagnosed with MLD using head magnetic resonance imaging and detecting a homozygous mutation of c.302G>A (p.Gly101Asp) in ARSA. Abdominal bloating was observed at the age of 4 years; CT revealed a giant tumor in the gallbladder and massive ascites. Cholecystectomy was performed and pathological examination revealed adenocarcinoma. Measurement of serum sulfatide revealed increased levels compared to the average healthy range. Discussion Rapidly increased ascites and large polyps which are reported as risk factors for cancer were characteristic in our MLD case. When such lesions are detected, they should be removed immediately because of the possibility of cancer, even in a pediatric patient.

Autophagy is a constitutive process that degrades, recycles and clears damaged proteins or organelles, yet, despite activation of this pathway, abnormal proteins accumulate in neurons in neurodegenerative diseases and in oligodendrocytes in white matter disorders. Here, we discuss the role of autophagy in white matter disorders, including neurotropic infections, inflammatory diseases such as multiple sclerosis, and in hereditary metabolic disorders and acquired toxic‐metabolic disorders. Once triggered due to cell stress, autophagy can enhance cell survival or cell death that may contribute to oligodendrocyte damage and myelin loss in white matter diseases. For some disorders, the mechanisms leading to myelin loss are clear, whereas the aetiological agent and pathological mechanisms are unknown for other myelin disorders, although emerging studies indicate that a common mechanism underlying these disorders is dysregulation of autophagic pathways. In this review we discuss the alterations in the autophagic process in white matter disorders and the potential use of autophagy‐modulating agents as therapeutic approaches in these pathological conditions. © 2020 The Authors. The Journal of Pathology published by John Wiley & Sons, Ltd. on behalf of The Pathological Society of Great Britain and Ireland.

Leukodystrophies are a broad spectrum of neurological disorders that are characterized primarily by deficiencies in myelin formation. Clinical manifestations of leukodystrophies usually appear during childhood and common symptoms include lack of motor coordination, difficulty with or loss of ambulation, issues with vision and/or hearing, cognitive decline, regression in speech skills, and even seizures. Many cases of leukodystrophy can be attributed to genetic mutations, but they have diverse inheritance patterns (e.g., autosomal recessive, autosomal dominant, or X-linked) and some arise from de novo mutations. In this review, we provide an updated overview of 35 types of leukodystrophies and focus on cellular mechanisms that may underlie these disorders. We find common themes in specialized functions in oligodendrocytes, which are specialized producers of membranes and myelin lipids. These mechanisms include myelin protein defects, lipid processing and peroxisome dysfunction, transcriptional and translational dysregulation, disruptions in cytoskeletal organization, and cell junction defects. In addition, non-cell-autonomous factors in astrocytes and microglia, such as autoimmune reactivity, and intercellular communication, may also play a role in leukodystrophy onset. We hope that highlighting these themes in cellular dysfunction in leukodystrophies may yield conceptual insights on future therapeutic approaches.

PRUNE1-related disorders manifest as severe neurodevelopmental conditions associated with neurodegeneration, implying a differential diagnosis at birth with static encephalopathies, and later with those manifesting progressive brain damage with the involvement of both the central and the peripheral nervous system.Here we report on another patient with PRUNE1 (p.Asp106Asn) recurrent mutation, whose leukodystrophy, inferior olives hyperintensity, and macrocephaly led to the misleading clinical suspicion of Alexander disease. Clinical features, together with other recent descriptions, suggest avoiding the term “microcephaly” in defining this disorder that could be renamed “neurodevelopmental disorder with progressive encephalopathy, hypotonia, and variable brain anomalies” (NPEHBA).

Leukodystrophies are a group of neurodegenerative genetic disorders that affect approximately 1 in 7500 individuals. Despite therapeutic progress in individual leukodystrophies, guidelines in neurologic care are sparse and consensus among physicians and caregivers remains a challenge. At patient advocacy meetings hosted by Hunter’s Hope from 2016-2018, multidisciplinary experts and caregivers met to conduct a literature review, identify knowledge gaps and summarize best practices regarding neurologic care. Stages of severity in leukodystrophies guided recommendations to address different levels of need based on a newly defined system of disease severity. Four core neurologic domains prioritized by families were identified and became the focus of this guideline: sleep, pain, seizures/epilepsy, and language/cognition. Based on clinical severity, the following categories were used: presymptomatic, early symptomatic, intermediate symptomatic, and advanced symptomatic. Across the leukodystrophies, neurologic care should be tailored to stages of severity while accounting for unique aspects of every disease and multiple knowledge gaps present. Standardized tools and surveys can help guide treatment but should not overburden families.

BACKGROUND: Multiple sulfatase deficiency (MSD) is an ultra-rare neurodegenerative disorder caused by pathogenic variants in SUMF1. This gene encodes formylglycine-generating enzyme (FGE), a protein required for sulfatase activation. The clinical course of MSD results from additive effect of each sulfatase deficiency, including metachromatic leukodystrophy (MLD), several mucopolysaccharidoses (MPS II, IIIA, IIID, IIIE, IVA, VI), chondrodysplasia punctata, and X-linked ichthyosis. While it is known that affected individuals demonstrate a complex and severe phenotype, the genotype-phenotype relationship and detailed clinical course is unknown.; METHODS: We report on 35 cases enrolled in our retrospective natural history study, n=32 with detailed histories. Neurologic function was longitudinally assessed with retrospective scales. Biochemical and computational modeling of novel SUMF1 variants was performed. Genotypes were classified based on predicted functional change, and each individual was assigned a genotype severity score.; RESULTS: The median age at symptom onset was 0.25years; median age at diagnosis was 2.7years; and median age at death was 13years. All individuals demonstrated developmental delay, and only a subset of individuals attained ambulation and verbal communication. All subjects experienced an accumulating systemic symptom burden. Earlier age at symptom onset and severe variant pathogenicity correlated with poor neurologic outcomes.; CONCLUSIONS: Using retrospective deep phenotyping and detailed variant analysis, we defined the natural history of MSD. We found that attenuated cases can be distinguished from severe cases by age of onset, attainment of ambulation, and genotype. Results from this study can help inform prognosis and facilitate future study design. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

Globoid cell leukodystrophy (GLD; Krabbe disease) is a progressive, incurable neurodegenerative disease caused by deficient activity of the hydrolytic enzyme galactosylceramidase (GALC). The ensuing cytotoxic accumulation of psychosine results in diffuse central and peripheral nervous system (CNS, PNS) demyelination. Presymptomatic hematopoietic stem cell transplantation (HSCT) is the only treatment for infantile-onset GLD; however, clinical outcomes of HSCT recipients often remain poor, and procedure-related morbidity is high. There are no effective therapies for symptomatic patients. Herein, we demonstrate in the naturally occurring canine model of GLD that presymptomatic monotherapy with intrathecal AAV9 encoding canine GALC administered into the cisterna magna increased GALC enzyme activity, normalized psychosine concentration, improved myelination, and attenuated inflammation in both the CNS and PNS. Moreover, AAV-mediated therapy successfully prevented clinical neurological dysfunction, allowing treated dogs to live beyond 2.5 years of age, more than 7 times longer than untreated dogs. Furthermore, we found that a 5-fold lower dose resulted in an attenuated form of disease, indicating that sufficient dosing is critical. Finally, postsymptomatic therapy with high-dose AAV9 also significantly extended lifespan, signifying a treatment option for patients for whom HSCT is not applicable. If translatable to patients, these findings would improve the outcomes of patients treated either pre- or postsymptomatically.

A 3-year-old girl presented with ataxia, dilated pupils, and behavioral change prompting work up for stroke. Her medical history included chronic mydriasis and patent ductus arteriosus requiring aortoplasty. Magnetic resonance imaging of the brain demonstrated confluent white matter signal abnormality concerning for leukodystrophy. Magnetic resonance angiography revealed a cerebral vessel arteriopathy with a “broomstick appearance” and other neuroradiographic findings consistent with ACTA2 mutation. Pathogenic Arg179His ACTA2 mutation was confirmed in the patient. ACTA2-related leukovasculopathy should be considered during workup of patients with abnormal white matter (eg, leukodystrophies), childhood stroke, and arteriopathies. Recognizing the combination of commonly associated physical and medical conditions associated with radiographic features of this neurogenetic condition will prompt appropriate care and screening for comorbidities associated with this disorder.

Genetically determined leukoencephalopathies comprise a group of rare inherited white matter disorders. The majority are progressive diseases resulting in early death. We performed a cross-sectional pilot study including 55 parents from 36 families to assess the level of stress experienced by parents of patients with genetically determined leukoencephalopathies, aged 1 month to 12 years. Thirty-four mothers and 21 fathers completed the Parenting Stress Index–4th Edition. One demographic questionnaire was completed per family. Detailed clinical data was gathered on all patients. Statistical analysis was performed with total stress percentile score as the primary outcome. Mothers and fathers had significantly higher stress levels compared with the normative sample; 20% of parents had high levels of stress whereas 11% had clinically significant levels of stress. Mothers and fathers had comparable total stress percentile scores. We identified pediatric behavioral difficulties and gross motor function to be factors influencing stress in mothers. Our study is the first to examine parental stress in this population and highlights the need for parental support early in the disease course. In this pilot study, we demonstrated that using the Parenting Stress Index–4th Edition to assess stress levels in parents of patients with genetically determined leukoencephalopathies is feasible, leads to valuable and actionable results, and should be used in larger, prospective studies.

Adrenoleukodystrophy (ALD) encompasses different neurological phenotypes, ranging from the most severe cerebral forms (C-ALD) to the less severe adrenomyeloneuropathy (AMN). As visual system can be varyingly involved, we aimed at exploring whether optical coherence tomography (OCT) may detect retinal abnormalities and their longitudinal changes in adult ALD patients. In this cross-sectional and longitudinal study, we measured the thicknesses of peripapillary retinal nerve fiber layer (pRNFL), macular ganglion cell complex (mGCC), and segmented inner and outer macula at baseline and their changes over time in 11 symptomatic adult ALD males and 10 age- and sex-matched healthy controls. Statistical analyses were performed for the patients as complete group, and splitting them into two subgroups, one (C-ALD) with and the other (AMN) without cerebral parieto-occipital white matter (WM) lesions. In the complete ALD group and in the C-ALD subgroup, the average pRNFL, mGCC, and inner macula were significantly thinner than in controls (p ≤ 0.01), whereas in the AMN subgroup, they were constantly, though non-significantly, thinner. Significant outer macula thinning was also observed (p

Hypomyelinating Leukodystrophies (HLDs) are a genetically heterogeneous, clinically overlapping group of disorders with the unifying MR imaging appearance of myelin deficit in the brain. In fact, it is the MRI phenotype that typically raises the diagnostic suspicion in this single largest group of undiagnosed leukodystrophies and guides gene testing for confirmation. This article reviews the neurobiology of myelination, focussing on the complex interplay of molecular genetic pathways and presents a practical clinico-radiological diagnostic algorithm based on the neuroimaging patterns of the common hypomyelinating disorders. The authors also address the current controversies about the definition and use of the term 'hypomyelination'.

TMEM106B encodes a lysosomal membrane protein and was initially identified as a risk factor for frontotemporal lobar degeneration. Recently, a dominant D252N mutation in TMEM106B was shown to cause hypomyelinating leukodystrophy. However, how TMEM106B regulates myelination is still unclear. Here we show that TMEM106B is expressed and localized to the lysosome compartment in oligodendrocytes. TMEM106B deficiency in mice results in myelination defects with a significant reduction of protein levels of proteolipid protein (PLP) and myelin oligodendrocyte glycoprotein (MOG), the membrane proteins found in the myelin sheath. The levels of many lysosome proteins are significantly decreased in the TMEM106B-deficient Oli-neu oligodendroglial precursor cell line. TMEM106B physically interacts with the lysosomal protease cathepsin D and is required to maintain proper cathepsin D levels in oligodendrocytes. Furthermore, we found that TMEM106B deficiency results in lysosome clustering in the perinuclear region and a decrease in lysosome exocytosis and cell surface PLP levels. Moreover, we found that the D252N mutation abolished lysosome enlargement and lysosome acidification induced by wild-type TMEM106B overexpression. Instead, it stimulates lysosome clustering near the nucleus as seen in TMEM106B-deficient cells. Our results support that TMEM106B regulates myelination through modulation of lysosome function in oligodendrocytes.

Krabbe disease is a progressive neurologic disorder caused by deficiency of the lysosomal enzyme galactocerebrosidase. The disease commonly has an early-infantile onset, but can have late-infantile, juvenile, or adult-onset phenotypes. Classic computed tomography (CT) and magnetic resonance imaging (MRI) findings in Krabbe have been well described. We report a patient, ultimately diagnosed with juvenile-onset Krabbe, who presented with atypical CT imaging and rapid disease progression. Our patient was a previously healthy and developmentally appropriate female who presented at 3 years 4 months of age with ataxia and motor regression that had progressed over the course of 6 weeks without an identifiable catalyst. CT, performed in the emergency setting, demonstrated extensive white matter hyperdensity. Subsequent MRI showed T2 hyperintensity of the white matter corresponding to the areas of hyperdensity on the CT, as well as enhancement of multiple cranial nerves bilaterally, suggestive of Krabbe disease. Enzymatic testing demonstrated low galactocerebrosidase activity and molecular testing of GALC revealed compound heterozygosity for 2 known pathogenic mutations, consistent with a diagnosis of Krabbe Disease. This included the common 30-kb deletion and a known pathogenic mutation associated with juvenile/adult-onset disease. Our patient’s diffuse hyperdensity on CT offers a new radiographic finding to include in the repertoire of Krabbe imaging, and thus aide in the diagnostic evaluation. The rapidity of progression our patient demonstrated is additionally unique and should be considered in the identification of juvenile Krabbe as well as the complicated decision-making process regarding potential treatments.

Pseudoexon inclusion caused by deep intronic variants is an important genetic cause for various disorders. Here, we present a case of a hypomyelinating leukodystrophy with developmental delay, intellectual disability, autism spectrum disorder, and hypodontia, which are consistent with autosomal recessive POLR3-related leukodystrophy. Whole-exome sequencing identified only a heterozygous missense variant (c.1451G>A) in POLR3A. To explore possible involvement of a deep intronic variant in another allele, we performed whole-genome sequencing of the patient with variant annotation by SpliceAI, a deep-learning-based splicing prediction tool. A deep intronic variant (c.645 + 312C>T) in POLR3A, which was predicted to cause inclusion of a pseudoexon derived from an Alu element, was identified and confirmed by mRNA analysis. These results clearly showed that whole-genome sequencing, in combination with deep-learning-based annotation tools such as SpliceAI, will bring us further benefits in detecting and evaluating possible pathogenic variants in deep intronic regions.

Iron-sulfur cluster assembly 2 (ISCA2)-related multiple mitochondrial dysfunction syndrome 4 (MMDS4) is a fatal autosomal recessive mitochondrial leukoencephalopathy. The disease typically manifests with rapid neurodevelopmental deterioration during the first months of life leading to a vegetative state and early death. MRI demonstrates a demyelinating leukodystrophy. We describe an eleven-year-old boy with a milder phenotype of ISCA2 related disorder manifesting as: normal early development, acute infantile neurologic deterioration leading to stable spastic quadriparesis, optic atrophy and mild cognitive impairment. The first MRI demonstrated a diffuse demyelinating leukodystrophy. A sequential MRI revealed white matter rarefaction with well-delineated cysts. The patient harbors two novel bi-allelic variants (p.Ala2Asp and p.Pro138Arg) in ISCA2 inherited from heterozygous carrier parents. This report expands the clinical spectrum of ISCA2-related disorders to include a milder phenotype with a longer life span and better psychomotor function and cavitating leukodystrophy on MRI. We discuss the possible genetic explanation for the different presentation.

Objective To examine disparities in the diagnosis of leukodystrophies including geographic factors and access to specialty centers. Study design Retrospective cohort study of pediatric patients admitted to Pediatric Health Information System hospitals. Patients with leukodystrophy were identified with International Classification of Diseases, Tenth Revision, Clinical Modification diagnostic codes for any of 4 leukodystrophies (X-linked adrenoleukodystrophy, Hurler disease, Krabbe disease, and metachromatic leukodystrophy). We used 3-level hierarchical generalized logistic modeling to predict diagnosis of a leukodystrophy based on distance traveled for hospital, neighborhood composition, urban/rural context, and access to specialty center. Results We identified 501 patients with leukodystrophy. Patients seen at a leukodystrophy center of excellence hospital were 1.73 times more likely to be diagnosed than patients at non-center of excellence hospitals. Patients who traveled farther were more likely to be diagnosed than those who traveled shorter. Patients living in a Health Professionals Shortage Area zip code were 0.86 times less likely to be diagnosed than those living in a non-Health Professionals Shortage Area zip code. Conclusions Geographic factors affect the diagnosis of leukodystrophies in pediatric patients, particularly in regard to access to a center with expertise in leukodystrophies. Our findings suggest a need for improving access to pediatric specialists and possibly deploying specialists or diagnostic testing more broadly.

Background Biallelic variants in POLR3A encoding the largest subunit of RNA polymerase III cause POLR3-related (or 4H) leukodystrophy characterized by neurologic dysfunction, abnormal dentition, endocrine abnormalities and ocular abnormality. Recently, whole-exome sequencing enabled the discovery of POLR3A variants in cases lacking diffuse hypomyelination, the principal MRI phenotype of POLR3-related leukodystrophy. Homozygous c.1771-6C > G variants in POLR3A were recently suggested to cause striatal and red nucleus involvement without white matter involvement. Case report: Here, we report three cases in two families with biallelic POLR3A variants. We identified two sets of compound heterozygous variants in POLR3A, c.1771-6C > G and c.791C > T, p.(Pro264Leu) for family 1 and c.1771-6C > G and c.2671C > T, p.(Arg891*) for family 2. Both families had the c.1771-6C > G variant, which led to aberrant mRNA splicing. Neuropsychiatric regression and severe intellectual disability were identified in three patients. Two cases showed dystonia and oligodontia. Notably, characteristic bilateral symmetric atrophy and abnormal signal of the striatum without diffuse white matter signal change were observed in brain MRI of all three individuals. Conclusions Striatum abnormalities may be another distinctive MRI finding associated with POLR3A variants, especially in cases including c.1771-6C > G variants and our cases can expand the phenotypic spectrum of POLR3A-related disorders.

EIF2AK1 and EIF2AK2 encode members of the eukaryotic translation initiation factor 2 alpha kinase (EIF2AK) family that inhibits protein synthesis in response to physiologic stress conditions. EIF2AK2 is also involved in innate immune response and the regulation of signal transduction, apoptosis, cell proliferation, and differentiation. Despite these findings, human disorders associated with deleterious variants in EIF2AK1 and EIF2AK2 have not been reported. Here, we describe the identification of nine unrelated individuals with heterozygous de novo missense variants in EIF2AK1 (1/9) or EIF2AK2 (8/9). Features seen in these nine individuals include white matter alterations (9/9), developmental delay (9/9), impaired language (9/9), cognitive impairment (8/9), ataxia (6/9), dysarthria in probands with verbal ability (6/9), hypotonia (7/9), hypertonia (6/9), and involuntary movements (3/9). Individuals with EIF2AK2 variants also exhibit neurological regression in the setting of febrile illness or infection. We use mammalian cell lines and proband-derived fibroblasts to further confirm the pathogenicity of variants in these genes and found reduced kinase activity. EIF2AKs phosphorylate eukaryotic translation initiation factor 2 subunit 1 (EIF2S1, also known as EIF2α), which then inhibits EIF2B activity. Deleterious variants in genes encoding EIF2B proteins cause childhood ataxia with central nervous system hypomyelination/vanishing white matter (CACH/VWM), a leukodystrophy characterized by neurologic regression in the setting of febrile illness and other stressors. Our findings indicate that EIF2AK2 missense variants cause a neurodevelopmental syndrome that may share phenotypic and pathogenic mechanisms with CACH/VWM.

Krabbe disease (KD), also known as globoid cell leukodystrophy disease, is an autosomal recessive lysosomal storage genetic disorder, which is caused by the deficiency of galactocerebrosidase (GALC) coding gene (GALC). This study aimed to use extensive computational pipelines in understanding the missense mutations in GALC. We retrieved 176 mutations from the public databases and subjected them to pathogenicity, stability, and conservation analyses. The PredictSNP, iStable, and ConSurf prediction tools predicted 45, 95, and 47 mutations to be deleterious, destabilizing, and highly conserved, respectively. The R396L and R396W were the most deleterious and destabilizing to GALC, and were therefore prioritized for further analysis. Systematic validation on the impact of the R396L and R396W mutations to the chaperone alpha lobeline was performed using the molecular docking approach. The docking analysis revealed that the mutant R396W interacted with minimal binding affinity compared with both the R396L mutant and native GALC. Furthermore, the repetitive molecular dynamics simulation analysis showed that the mutant R396W demonstrated less compactness and reduced number of intramolecular hydrogen bonds compared with the mutant R396L and the native GALC. Overall, we observed higher structural and functional modifications in R396W positioned in the substrate-binding site. This was highly supported by the MMPBSA and DSSP analysis of the GROMACS. DSSP showed the transformation of turns to bends, indicating a loss of stability due to the R396W mutation. This study is expected to serve as a platform for prioritizing mutant proteins that could be a platform for both drug and target therapeuticsCommunicated by Ramaswamy H. Sarma.

The contribution of microglia in neurological disorders is emerging as a leading disease driver rather than a consequence of pathology. RNAseT2‐deficient leukoencephalopathy is a severe childhood white matter disorder affecting patients in their first year of life and mimicking a cytomegalovirus brain infection. The early onset and resemblance of the symptoms to a viral infection suggest an inflammatory and embryonic origin of the pathology. There are no treatments available for this disease as our understanding of the cellular drivers of the pathology are still unknown. In this study, using a zebrafish mutant for the orthologous rnaset2 gene, we have identified an inflammatory signature in early development and an antiviral immune response in mature adult brains. Using the optical transparency and the ex utero development of the zebrafish larvae we studied immune cell behavior during brain development and identified abnormal microglia as an early marker of pathology. Live imaging and electron microscopy identified that mutant microglia displayed an engorged morphology and were filled with undigested apoptotic cells and undigested substrate. Using microglia‐specific depletion and rescue experiments, we identified microglia as drivers of this embryonic phenotype and potential key cellular player in the pathology of RNAseT2‐deficient leukoencephalopathy. Our zebrafish model also presented with reduced survival and locomotor defects, therefore recapitulating many aspects of the human disease. Our study therefore placed our rnaset2 mutant at the forefront of leukodystrophy preclinical models and highlighted tissue‐specific approaches as future therapeutic avenues., Main Points Loss of rnaset2 results in inflammation and lysosomal‐deficient microglia failing to digest dying neurons.Targeting microglia restores embryonic microglial defects to clear neurodevelopmental apoptosis.Mutants have reduced survival and locomotor defects.

The overlapping clinical and neuroimaging phenotypes of leukodystrophies pose a diagnostic challenge to both clinicians and researchers alike. Studies on the application of exome sequencing in the diagnosis of leukodystrophies are emerging. We used targeted gene panel sequencing of 6440 genes to investigate the genetic etiology in a cohort of 50 children with neuroimaging diagnosis of leukodystrophy/genetic leukoencephalopathy of unknown etiology. These 50 patients without a definite biochemical or genetic diagnosis were derived from a cohort of 88 patients seen during a 2.5-year period (2015 January-2017 June). Patients who had diagnosis by biochemical or biopsy confirmation (n = 17) and patients with incomplete data or lack of follow-up (n = 21) were excluded. Exome sequencing identified variants in 30 (60%) patients, which included pathogenic or likely pathogenic variants in 28 and variants of unknown significance in 2. Among the patients with pathogenic or likely pathogenic variants, classic leukodystrophies constituted 13 (26%) and genetic leukoencephalopathies 15 (30%). The clinical and magnetic resonance imaging (MRI) findings and genetic features of the identified disorders are discussed.