Improving newborn screening test performance for metachromatic leukodystrophy: Recommendation from a pre-pilot study that identified a late-infantile case for treatment.

Metachromatic leukodystrophy (MLD) is a devastating rare neurodegenerative disease. Typically, loss of motor and cognitive skills precedes early death. The disease is characterised by deficient lysosomal arylsulphatase A (ARSA) activity and an accumulation of undegraded sulphatide due to pathogenic variants in the ARSA gene. Atidarsagene autotemcel (arsa-cel), an ex vivo haematopoietic stem cell gene therapy was approved for use in the UK in 2021 to treat early-onset forms of pre- or early-symptomatic MLD. Optimal outcomes require early diagnosis, but in the absence of family history this is difficult to achieve without newborn screening (NBS). A pre-pilot MLD NBS study was conducted as a feasibility study in Manchester UK using a two-tiered screening test algorithm. Pre-established cutoff values (COV) for the first-tier C16:0 sulphatide (C16:0-S) and the second-tier ARSA tests were evaluated. Before the pre-pilot study, initial test validation using non­neonatal diagnostic bloodspots demonstrated ARSA pseudodeficiency status was associated with normal C16:0-S results for age (n = 43) and hence not expected to cause false positive results in this first-tier test. Instability of ARSA in bloodspot required transfer of NBS bloodspots from ambient temperature to -20°C storage within 7-8 days after heel prick, the earliest possible in this UK pre-pilot study. Eleven of 3687 de-identified NBS samples in the pre-pilot were positive for C16:0-S based on the pre-established COV of ≥170 nmol/l or ≥ 1.8 multiples of median (MoM). All 11 samples were subsequently tested negative determined by the ARSA COV of <20% mean of negative controls. However, two of 20 NBS samples from MLD patients would be missed by this C16:0-S COV. A further suspected false negative case that displayed 4% mean ARSA activity by single ARSA analysis for the initial test validation was confirmed by genotyping of this NBS bloodspot, a severe late infantile MLD phenotype was predicted. This led to urgent assessment of this child by authority approval and timely commencement of arsa-cel gene therapy at 11 months old. Secondary C16:0-S analysis of this NBS bloodspot was 150 nmol/l or 1.67 MoM. This was the lowest result reported thus far, a new COV of 1.65 MoM is recommended for future pilot studies. Furthermore, preliminary data of this study showed C16:1-OH sulphatide is more specific for MLD than C16:0-S. In conclusion, this pre-pilot study adds to the international evidence that recommends newborn screening for MLD, making it possible for patients to benefit fully from treatment through early diagnosis.

Newborn screening in metachromatic leukodystrophy - European consensus-based recommendations on clinical management.

INTRODUCTION: Metachromatic leukodystrophy (MLD) is a rare autosomal recessive lysosomal storage disorder resulting from arylsulfatase A enzyme deficiency, leading to toxic sulfatide accumulation. As a result affected individuals exhibit progressive neurodegeneration. Treatments such as hematopoietic stem cell transplantation (HSCT) and gene therapy are effective when administered pre-symptomatically. Newborn screening (NBS) for MLD has recently been shown to be technically feasible and is indicated because of available treatment options. However, there is a lack of guidance on how to monitor and manage identified cases. This study aims to establish consensus among international experts in MLD and patient advocates on clinical management for NBS-identified MLD cases. METHODS: A real-time Delphi procedure using eDELPHI software with 22 experts in MLD was performed. Questions, based on a literature review and workshops, were answered during a seven-week period. Three levels of consensus were defined: A) 100%, B) 75-99%, and C) 50-74% or >75% but >25% neutral votes. Recommendations were categorized by agreement level, from strongly recommended to suggested. Patient advocates participated in discussions and were involved in the final consensus. RESULTS: The study presents 57 statements guiding clinical management of NBS-identified MLD patients. Key recommendations include timely communication by MLD experts with identified families, treating early-onset MLD with gene therapy and late-onset MLD with HSCT, as well as pre-treatment monitoring schemes. Specific knowledge gaps were identified, urging prioritized research for future evidence-based guidelines. DISCUSSION: Consensus-based recommendations for NBS in MLD will enhance harmonized management and facilitate integration in national screening programs. Structured data collection and monitoring of screening programs are crucial for evidence generation and future guideline development. Involving patient representatives in the development of recommendations seems essential for NBS programs.

Inventory of current practices regarding hematopoietic stem cell transplantation in metachromatic leukodystrophy in Europe and neighboring countries.

BACKGROUND: For decades, early allogeneic stem cell transplantation (HSCT) has been used to slow neurological decline in metachromatic leukodystrophy (MLD). There is lack of consensus regarding who may benefit, and guidelines are lacking. Clinical practice relies on limited literature and expert opinions. The European Reference Network for Rare Neurological Diseases (ERN-RND) and the MLD initiative facilitate expert panels for treatment advice, but some countries are underrepresented. This study explores organizational and clinical HSCT practices for MLD in Europe and neighboring countries to enhance optimization and harmonization of cross-border MLD care. METHODS: A web-based EUSurvey was distributed through the ERN-RND and the European Society for Blood and Marrow Transplantation Inborn Errors Working Party. Personal invitations were sent to 89 physicians (43 countries) with neurological/metabolic/hematological expertise. The results were analyzed and visualized using Microsoft Excel and IBM SPSS statistics. RESULTS: Of the 30 countries represented by 42 respondents, 23 countries offer HSCT for MLD. The treatment is usually available in 1-3 centers per country (18/23, 78%). Most countries have no or very few MLD patients transplanted during the past 1-5 years. The eligibility criteria regarding MLD subtype, motor function, IQ, and MRI largely differ across countries. CONCLUSION: HSCT for MLD is available in most European countries, but uncertainties exist in Eastern and South-Eastern Europe. Applied eligibility criteria and management vary and may not align with the latest scientific insights, indicating physicians' struggle in providing evidence-based care. Interaction between local physicians and international experts is crucial for adequate treatment decision-making and cross-border care in the rapidly changing MLD field.

Allogeneic hematopoietic cell transplantation for adult metachromatic leukodystrophy: a case series.

ABSTRACT: Metachromatic leukodystrophy (MLD) is a rare genetic disorder caused by pathogenic variants of the ARSA gene, leading to a deficiency of the arylsulfatase A enzyme (ARSA) and consecutive accumulation of galactosylceramide-3-0-sulfate in the nervous system. The condition leads to severe neurological deficits and subsequently results in profound intellectual and motoric disability. Especially, the adult form of MLD, which occurs in individuals aged >16 years, poses significant challenges for treating physicians because of the rarity of cases, limited therapeutic options, and different allogeneic hematopoietic cell transplantation (allo-HCT) protocols worldwide. Here, we report the results of allo-HCT treatment in 4 patients with a confirmed adult MLD diagnosis. Bone marrow or mobilized peripheral progenitor cells were infused after a reduced intensity conditioning regime consisting of fludarabine and treosulfan. In 3 patients, allo-HCT was followed by an infusion of mesenchymal cells to further consolidate ARSA production. We observed a good tolerability and an increase in ARSA levels up to normal range values in all patients. A full donor chimerism was detected in 3 patients within the first 12 months. In a 1-year follow-up, patients with complete donor chimerism showed a neurological stable condition. Only 1 patient with an increasing autologous chimerism showed neurological deterioration and a decline in ARSA levels in the first year. In summary, allo-HCT offers a therapeutic option for reconstituting ARSA enzyme levels in adult patients with MLD, with tolerable side effects.

Progress in leukodystrophies with zebrafish.

Inherited leukodystrophies are genetic disorders characterized by abnormal white matter in the central nervous system. Although individually rare, there are more than 400 distinct types of leukodystrophies with a cumulative incidence of 1 in 4500 live births. The pathophysiology of most leukodystrophies is poorly understood, there are treatments for only a few, and there is significant morbidity and mortality, suggesting a critical need for improvements in this field. A variety of animal, cell, and induced pluripotent stem cell-derived models have been developed for leukodystrophies, but with significant limitations in all models. Many leukodystrophies lack animal models, and extant models often show no or mixed recapitulation of key phenotypes. Zebrafish (Danio rerio) have become increasingly used as disease models for studying leukodystrophies due to their early onset of disease phenotypes and conservation of molecular and neurobiological mechanisms. Here, we focus on reviewing new zebrafish disease models for leukodystrophy or models with recent progress. This includes discussion of leukodystrophy with vanishing white matter disease, X-linked adrenoleukodystrophy, Zellweger spectrum disorders and peroxisomal disorders, PSAP deficiency, metachromatic leukodystrophy, Krabbe disease, hypomyelinating leukodystrophy-8/4H leukodystrophy, Aicardi-Goutières syndrome, RNASET2-deficient cystic leukoencephalopathy, hereditary diffuse leukoencephalopathy with spheroids-1 (CSF1R-related leukoencephalopathy), and ultra-rare leukodystrophies. Zebrafish models offer important potentials for the leukodystrophy field, including testing of new variants in known genes; establishing causation of newly discovered genes; and early lead compound identification for therapies. There are also unrealized opportunities to use humanized zebrafish models which have been sparsely explored.

Elucidating the Therapeutic Utility of Olaparib in Sulfatide-Induced Human Astrocyte Toxicity and Neuroinflammation.

Metachromatic leukodystrophy (MLD) is a severe demyelinating, autosomal recessive genetic leukodystrophy, with no curative treatment. The disease is underpinned by mutations in the arylsulfatase A gene (ARSA), resulting in deficient activity of this lysosomal enzyme, and consequential accumulation of galactosylceramide-3-O-sulfate (sulfatide) in the brain. Most of the effects in the brain have been attributed to the accumulation of sulfatides in oligodendrocytes and their cell damage. In contrast, less is known regarding sulfatide toxicity in astrocytes. Poly (ADP-ribose) polymerase (PARP) inhibitors are anti-cancer therapeutics that have proven efficacy in preclinical models of many neurodegenerative and inflammatory diseases, but have never been tested for MLD. Here, we examined the toxic effect of sulfatides on human astrocytes and restoration of this cell damage by the marketed PARP-1 inhibitor, Olaparib. Cultured human astrocytes were treated with increasing concentrations of sulfatides (5-100 µM) with or without Olaparib (100 nM). Cell viability assays were used to ascertain whether sulfatide-induced toxicity was rescued by Olaparib. Immunofluorescence, calcium (Ca2+) imaging, ROS, and mitochondrial damage assays were also used to explore the effects of sulfatides and Olaparib. ELISAs were performed and chemotaxis of peripheral blood immune cells was measured to examine the effects of Olaparib on sulfatide-induced inflammation in human astrocytes. Here, we established a concentration-dependent (EC50∼20 µM at 24 h) model of sulfatide-induced astrocyte toxicity. Our data demonstrate that sulfatide-induced astrocyte toxicity involves (i) PARP-1 activation, (ii) pro-inflammatory cytokine release, and (iii) enhanced chemoattraction of peripheral blood immune cells. Moreover, these sulfatide-induced effects were attenuated by Olaparib (IC50∼100 nM). In addition, sulfatide caused impairments of ROS production, mitochondrial stress, and Ca2+ signaling in human astrocytes, that were indicative of metabolic alterations and that were also alleviated by Olaparib (100 nM) treatment. Our data support the hypothesis that sulfatides can drive astrocyte cell death and demonstrate that Olaparib can dampen many facets of sulfatide-induced toxicity, including, mitochondrial stress, inflammatory responses, and communication between human astrocytes and peripheral blood immune cells. These data are suggestive of potential therapeutic utility of PARP inhibitors in the sphere of rare demyelinating diseases, and in particular MLD. Graphical abstract. Proposed mechanism of action of Olaparib in sulfatide-treated astrocytes. Human astrocytes treated for 24 h with sulfatides increase PARP-1 expression and die. PARP-1 overexpression is modulated by Ca2+ release from the endoplasmic reticulum, thus enhancing intracellular Ca2+ concentration. PARP-1 inhibition with Olaparib reduces Ca2+ influx and cell death. Olaparib also decreases IL-6, IL-8, IL-17, and CX3CL1 release from sulfatide-stimulated astrocytes, suggesting that PARP-1 plays a role in dampening neuroinflammation in MLD. This is confirmed by the reduction of immune cell migration such as lymphocytes, NK cells, and T cells towards sulfatide-treated astrocytes. Moreover, mitochondrial stress and ROS production induced by sulfatides are rescued by PARP-1 inhibition. Future studies will focus on the signaling cascades triggered by PARP-1-mediated currents in reactive astrocytes and Olaparib as a potential therapeutic target for MLD.

A systematic review of clinical effectiveness and safety for historical and current treatment options for metachromatic leukodystrophy in children, including atidarsagene autotemcel.

OBJECTIVE: To understand the benefit-risk profile for historical and current treatments for MLD. METHODS: A systematic review was conducted on the effectiveness, safety, and costs of MLD treatments: allogeneic haematopoietic stem cell transplantation (HSCT) and atidarsagene autotemcel (arsa-cel) according to best practice. RESULTS: A total of 6940 titles and abstracts were retrieved from the literature searches and 26 from other sources. From these, 35 manuscripts reporting on a total of 12 studies were selected for inclusion in the review. There were no controlled multi-armed trials. However, we provide observations comparing two interventional therapies (alloHSCT and arsa-cel) and each of these to standard/supportive care (natural history). There were no benefits for survival, gross motor function and cognitive function for LI patients receiving alloHSCT, as patients experienced disease progression similar to LI natural history. For juvenile patients receiving alloHSCT, no differences in survival were observed versus natural history, however stabilisation of cognitive and motor function were reported for some patients (particularly for pre- or minimally-symptomatic LJ patients), while others experienced disease progression. Furthermore, alloHSCT was associated with severe complications such as treatment-related mortality, graft versus host disease, and re-transplantation in both LI and EJ treated patients. Most LI and EJ patients treated with arsa-cel appeared to have normal development, preservation, or slower progression of gross motor function and cognitive function, in contrast to the rapid decline observed in natural history patients. A survival benefit for arsa-cel versus natural history and versus alloHSCT was observed in LI patients.LI and EJ patients treated with arsa-cel had better gross motor function and cognitive function compared to alloHSCT, which had limited effect on motor and cognitive decline. No data has been reported for arsa-cel treatment of LJ patients. CONCLUSIONS: Overall, this systematic review indicates that compared to NHx and HSCT, treatment with arsa-cel results in clinically relevant benefits in LI and EJ MLD patients by preserving cognitive function and motor development in most patients, and increased survival for LI patients. Nevertheless, further research is required to confirm these findings, given they are based on results from non-RCT studies.

Engineered arylsulfatase A with increased activity, stability and brain delivery for therapy of metachromatic leukodystrophy.

A deficiency of human arylsulfatase A (hASA) causes metachromatic leukodystrophy (MLD), a lysosomal storage disease characterized by sulfatide accumulation and central nervous system (CNS) demyelination. Efficacy of enzyme replacement therapy (ERT) is increased by genetic engineering of hASA to elevate its activity and transfer across the blood-brain barrier (BBB), respectively. To further improve the enzyme's bioavailability in the CNS, we mutated a cathepsin cleavage hot spot and obtained hASAs with substantially increased half-lives. We then combined the superstabilizing exchange E424A with the activity-promoting triple substitution M202V/T286L/R291N and the ApoEII-tag for BBB transfer in a trimodal modified neoenzyme called SuPerTurbo-ASA. Compared with wild-type hASA, half-life, activity, and M6P-independent uptake were increased more than 7-fold, about 3-fold, and more than 100-fold, respectively. ERT of an MLD-mouse model with immune tolerance to wild-type hASA did not induce antibody formation, indicating absence of novel epitopes. Compared with wild-type hASA, SuPerTurbo-ASA was 8- and 12-fold more efficient in diminishing sulfatide storage of brain and spinal cord. In both tissues, storage was reduced by ∼60%, roughly doubling clearance achieved with a 65-fold higher cumulative dose of wild-type hASA previously. Due to its enhanced therapeutic potential, SuPerTurbo-ASA might be a decisive advancement for ERT and gene therapy of MLD.

Evaluating meaningful changes in physical functioning and cognitive declines in metachromatic leukodystrophy: a caregiver interview study.

BACKGROUND: Metachromatic leukodystrophy (MLD) is a rare lysosomal storage disease caused by deficient activity of arylsulfatase A (ASA). Treatment options for patients are limited; gene therapy based on haematopoietic stem cell transplantation is the only approved treatment for some subtypes of MLD. Any therapeutic benefit of treatments must be meaningful for patients and their families. We evaluated the clinical meaningfulness of slowing the decline in gross motor function as measured by the Gross Motor Function Classification in MLD (GMFC-MLD) from the caregiver perspective via semi-structured telephone interviews with caregivers of children with late-infantile MLD. We also evaluated the perceived significance of declines in communication abilities measured by the Expressive Language Function Classification in MLD (ELFC-MLD). This work could help to inform the endpoints of a phase 2 clinical trial (NCT03771898) assessing the efficacy of intrathecal recombinant human ASA in MLD. RESULTS: Twelve caregivers were recruited, reporting on 12 children with MLD. Children had a mean age of 6.1 years; mean age at symptom onset was 17.6 months. Most children (10/12) progressed from walking without support (categories 0-1) to a loss of locomotion (categories 5-6) in ≤ 2 years. Caregivers felt that GMFC-MLD and ELFC-MLD accurately described motor and language declines in their children, respectively. Most caregivers (10/12) reported that the idea of delaying disease progression would be meaningful. Further, a slowing of motor function decline in GMFC-MLD, from category 1 to category 3 or from category 2 to category 4 over 2 years, was seen as meaningful by all caregivers asked; however, only 3/12 caregivers reported that delayed decline would be meaningful if baseline category was ≥ 3. Caregivers also reported that delaying expressive language decline at any level that did not indicate a complete loss of expressive language (indicated by categories 1-3) would be meaningful. CONCLUSIONS: Caregivers of children with MLD felt that a delayed decline in gross motor function, as assessed by the GMFC-MLD, would be meaningful, supporting the selection of primary and secondary endpoints for the phase 2 clinical trial. Communication abilities were another area of significance for consideration in future clinical trial design.

Neurodegenerative disease after hematopoietic stem cell transplantation in metachromatic leukodystrophy.

OBJECTIVE: Metachromatic leukodystrophy is a lysosomal storage disease caused by deficient arylsulfatase A. It is characterized by progressive demyelination and thus mainly affects the white matter. Hematopoietic stem cell transplantation may stabilize and improve white matter damage, yet some patients deteriorate despite successfully treated leukodystrophy. We hypothesized that post-treatment decline in metachromatic leukodystrophy might be caused by gray matter pathology. METHODS: Three metachromatic leukodystrophy patients treated with hematopoietic stem cell transplantation with a progressive clinical course despite stable white matter pathology were clinically and radiologically analyzed. Longitudinal volumetric MRI was used to quantify atrophy. We also examined histopathology in three other patients deceased after treatment and compared them with six untreated patients. RESULTS: The three clinically progressive patients developed cognitive and motor deterioration after transplantation, despite stable mild white matter abnormalities on MRI. Volumetric MRI identified cerebral and thalamus atrophy in these patients, and cerebellar atrophy in two. Histopathology showed that in brain tissue of transplanted patients, arylsulfatase A expressing macrophages were clearly present in the white matter, but absent in the cortex. Arylsulfatase A expression within patient thalamic neurons was lower than in controls, the same was found in transplanted patients. INTERPRETATION: Neurological deterioration may occur after hematopoietic stem cell transplantation in metachromatic leukodystrophy despite successfully treated leukodystrophy. MRI shows gray matter atrophy, and histological data demonstrate absence of donor cells in gray matter structures. These findings point to a clinically relevant gray matter component of metachromatic leukodystrophy, which does not seem sufficiently affected by transplantation.

Single Systemic Administration of a Gene Therapy Leading to Disease Treatment in Metachromatic Leukodystrophy Arsa Knock-Out Mice.

Metachromatic leukodystrophy (MLD) is a rare, inherited, demyelinating lysosomal storage disorder caused by mutations in the arylsulfatase-A gene (ARSA). In patients, levels of functional ARSA enzyme are diminished and lead to deleterious accumulation of sulfatides. Herein, we demonstrate that intravenous administration of HSC15/ARSA restored the endogenous murine biodistribution of the corresponding enzyme, and overexpression of ARSA corrected disease biomarkers and ameliorated motor deficits in Arsa KO mice of either sex. In treated Arsa KO mice, when compared with intravenously administered AAV9/ARSA, significant increases in brain ARSA activity, transcript levels, and vector genomes were observed with HSC15/ARSA Durability of transgene expression was established in neonate and adult mice out to 12 and 52 weeks, respectively. Levels and correlation between changes in biomarkers and ARSA activity required to achieve functional motor benefit was also defined. Finally, we demonstrated blood-nerve, blood-spinal and blood-brain barrier crossing as well as the presence of circulating ARSA enzyme activity in the serum of healthy nonhuman primates of either sex. Together, these findings support the use of intravenous delivery of HSC15/ARSA-mediated gene therapy for the treatment of MLD.SIGNIFICANCE STATEMENT Herein, we describe the method of gene therapy adeno-associated virus (AAV) capsid and route of administration selection leading to an efficacious gene therapy in a mouse model of metachromatic leukodystrophy. We demonstrate the therapeutic outcome of a new naturally derived clade F AAV capsid (AAVHSC15) in a disease model and the importance of triangulating multiple end points to increase the translation into higher species via ARSA enzyme activity and biodistribution profile (with a focus on the CNS) with that of a key clinically relevant biomarker.

Atidarsagene autotemcel for metachromatic leukodystrophy.

Metachromatic leukodystrophy (MLD) is a rare autosomal recessive disorder of sphingolipid metabolism, due to a deficiency of the enzyme arylsulfatase A (ARSA). The main clinical signs of the disease are secondary to central and peripheral nervous system demyelination. MLD is subdivided into early- and late-onset subtypes based upon the onset of neurological disease. The early-onset subtype is associated with a more rapid progression of the disease that leads to death within the first decade of life. Until recently, no effective treatment was available for MLD. The blood-brain barrier (BBB) prevents systemically administered enzyme replacement therapy from reaching target cells in MLD. The evidence for the efficacy of hematopoietic stem cell transplantation is limited to the late-onset MLD subtype. Here, we review the preclinical and clinical studies that facilitated the approval of the ex vivo gene therapy atidarsagene autotemcel for early-onset MLD by the European Medicines Agency (EMA) in December 2020. This approach was studied in an animal model first and then in a clinical trial, eventually proving its efficacy in preventing disease manifestations in presymptomatic patients and stabilizing its progression in paucisymptomatic subjects. This new therapeutic consists of patients' CD34+ hematopoietic stem/progenitor cells (HSPCs) transduced with a lentiviral vector encoding functional ARSA cDNA. The gene-corrected cells get reinfused into the patients after a cycle of chemotherapy conditioning.

Experiences of patients and their family members with metachromatic leukodystrophy, adrenoleukodystrophy, and Krabbe disease: a qualitative systematic review protocol.

OBJECTIVE: The objective of this review is to synthesize the experiences of patients with metachromatic leukodystrophy (MLD), adrenoleukodystrophy (ALD), and Krabbe disease and the experiences of their family members. INTRODUCTION: MLD, ALD, and Krabbe disease are rare disorders that are classified as lysosomal storage or peroxisomal disorders, with similar presentations as leukodystrophy. As these diseases cause cognitive and neurological decline due to the progression of leukodystrophy associated with demyelination, they have significant impact on the lives of patients and their families. It is important to identify the impact and challenges of these diseases on patients' lives and on their families, as well as to synthesize qualitative studies regarding their experiences. INCLUSION CRITERIA: We will consider studies including patients with MLD, ALD, or Krabbe disease and their family members. These experiences will include the challenges, dissatisfactions, and frustrations with symptoms and treatments; complications of hematopoietic stem cell transplantation; and the increased caregiver burden with disease progression. This is important since the impacts of disease progression are experienced in a variety of settings beyond the hospital, such as in the community and at home. METHODS: The search strategy will follow JBI methodology and be conducted in 3 steps: an initial limited search, a comprehensive database search, and a reference search of the included articles. MEDLINE, CINAHL Plus, PsycINFO, and Scopus will be searched with no restriction on language or publication dates. The study selection, critical appraisal, data extraction, and data synthesis will be performed according to JBI guidelines for systematic reviews of qualitative research. Final syntheses will be assessed using the ConQual approach. SYSTEMATIC REVIEW REGISTRATION NUMBER: PROSPERO CRD42022318805.

Understanding caregiver descriptions of initial signs and symptoms to improve diagnosis of metachromatic leukodystrophy.

BACKGROUND: Metachromatic leukodystrophy (MLD), a relentlessly progressive and ultimately fatal condition, is a rare autosomal recessive lysosomal storage disorder caused by a deficiency of the enzyme arylsulfatase A (ARSA). Historically management has been palliative or supportive care. Hematopoietic stem cell transplantation is poorly effective in early-onset MLD and benefit in late-onset MLD remains controversial. Hematopoietic stem cell gene therapy, Libmeldy (atidarsagene autotemcel), was recently approved by the European Medicines Agency for early-onset MLD. Treatment benefit is mainly observed at an early disease stage, indicating the need for early diagnosis and intervention. This study contributes insights into the caregiver language used to describe initial MLD symptomatology, and thereby aims to improve communication between clinicians and families impacted by this condition and promote a faster path to diagnosis. RESULTS: Data was collected through a moderator-assisted online 60-min survey and 30-min semi-structured follow-up telephone interview with 31 MLD caregivers in the United States (n = 10), France (n = 10), the United Kingdom (n = 5), and Germany (n = 6). All respondents were primary caregivers of a person with late infantile (n = 20), juvenile (n = 11) or borderline late infantile/juvenile (n = 1) MLD (one caregiver reported for 2 children leading to a sample of 32 individuals with MLD). Caregivers were asked questions related to their child's initial signs and symptoms, time to diagnosis and interactions with healthcare providers. These results highlight the caregiver language used to describe the most common initial symptoms of MLD and provide added context to help elevate the index of suspicion of disease. Distinctions between caregiver descriptions of late infantile and juvenile MLD in symptom onset and disease course were also identified. CONCLUSIONS: This study captures the caregiver description of the physical, behavioral, and cognitive signs of MLD prior to diagnosis. The understanding of the caregiver language at symptom onset sheds light on a critical window of often missed opportunity for earlier diagnosis and therapeutic intervention in MLD.

Clinical Reasoning: A 23-Year-Old Woman Presenting With Cognitive Impairment and Gait Disturbance.

Metachromatic leukodystrophy (MLD) is a rare inherited lysosomal disorder. The condition progresses relentlessly, with severe disability typically established within 6-14 years of symptom onset. There is no cure, and limited treatment options are available to slow disease progression. We describe the case of a 23-year-old woman with forgetfulness, unsteady gait, and falls. Neurologic examination revealed intermittent dystonic posturing of the right upper and lower limb when walking. The Addenbrooke's Cognitive Examination (ACE) score was 70/100. MRI sequences demonstrated frontal-predominant atrophy and extensive white matter hyperintensity. Differential diagnoses such as autoimmune, inflammatory, and neoplastic diseases were excluded, and a genetic diagnosis was considered. Lysosomal enzyme testing showed low arylsulfatase with elevated urinary sulfatides, and genetic testing revealed a homozygous pathogenic mutation in the ARSA gene securing a diagnosis of adult-onset MLD. A male sibling also had early cognitive impairment and was found to have the same mutation. Hematopoietic stem cell transplantation (HSCT) was offered after discussion with experts. The male sibling died of multiple complications after HSCT. The index patient is now 24 months after HSCT, and disease progression has halted. This case highlights the challenges in the accurate diagnosis of adult-onset leukoencephalopathies and explores potential treatment strategies. A stepwise approach to the differential diagnosis of white matter diseases is demonstrated. HSCT may be an effective treatment, but the significant complication rate needs to be carefully considered.

Hematopoietic Stem Cell Transplantation with Mesenchymal Stromal Cells in Children with Metachromatic Leukodystrophy.

Metachromatic leukodystrophy (MLD) is a lysosomal storage disorder primarily affecting the white matter of the nervous system that results from a deficiency of the arylsulfatase A (ARSA). Mesenchymal stem cells (MSCs) are able to secrete ARSA and have shown beneficial effects in MLD patients. In this retrospective analysis, 10 pediatric MLD patients [mesenchymal stem cell group (MSCG)] underwent allogeneic hematopoietic stem cell transplantation (HSCT) and received two applications of 2 × 106 MSCs/kg bodyweight at day +30 and +60 after HSCT between 2007 and 2018. MSC safety, occurrence of graft-versus-host disease (GvHD), blood ARSA levels, chimerism, cell regeneration and engraftment, magnetic resonance imaging (MRI) changes, and the gross motor function were assessed within the first year of HSCT. The long-term data included clinical outcomes and safety aspects of MSCs. Data were compared to a control cohort of seven pediatric MLD patients [control group (CG)] who underwent HSCT only. The application of MSC in pediatric MLD patients after allogeneic HSCT was safe and well tolerated, and long-term potentially MSC-related adverse effects up to 13.5 years after HSCT were not observed. Patients achieved significantly higher ARSA levels (CG: median 1.03 nmol·10-6 and range 0.41-1.73 | MSCG: median 1.58 nmol·10-6 and range 0.44-2.6; P < 0.05), as well as significantly higher leukocyte (P < 0.05) and thrombocyte (P < 0.001) levels within 365 days of MSC application compared to CG patients. Statistically significant effects on acute GvHD, regeneration of immune cells, MRI changes, gross motor function, and clinical outcomes were not detected. In conclusion, the application of MSCs in pediatric MLD patients after allogeneic HSCT was safe and well tolerated. The two applications of 2 × 106/kg allogeneic MSCs were followed by improved engraftment and hematopoiesis within the first year after HSCT. Larger, prospective trials are necessary to evaluate the impact of MSC application on engraftment and hematopoietic recovery.