Consensus guidelines for newborn screening, diagnosis and treatment of infantile Krabbe disease

Impact of an irreversible β-galactosylceramidase inhibitor on the lipid profile of zebrafish embryos

Krabbe disease is a sphingolipidosis characterized by the genetic deficiency of the acid hydrolase β-galactosylceramidase (GALC). Most of the studies concerning the biological role of GALC performed on Krabbe patients and Galc-deficient twitcher mice (an authentic animal model of the disease) indicate that the pathogenesis of this disorder is the consequence of the accumulation of the neurotoxic GALC substrate β-galactosylsphingosine (psychosine), ignoring the possibility that this enzyme may exert a wider biological impact. Indeed, limited information is available about the effect of GALC downregulation on the cell lipidome in adult and developing organisms. The teleost zebrafish (Danio rerio) has emerged as a useful platform to model human genetic diseases, including sphingolipidoses, and two GALC co-orthologs have been identified in zebrafish (galca and galcb). Here, we investigated the effect of the competitive and irreversible GALC inhibitor β-galactose-cyclophellitol (GCP) on the lipid profile of zebrafish embryos. Molecular modelling indicates that GCP can be sequestered in the catalytic site of the enzyme and covalently binds human GALC, and the zebrafish Galca and Galcb proteins in a similar manner. Accordingly, GCP inhibits the β-galactosylceramide hydrolase activity of zebrafish in vitro and in vivo, leading to significant alterations of the lipidome of zebrafish embryos. These results indicate that the lack of GALC activity deeply affects the lipidome during the early stages of embryonic development, and thereby provide insights into the pathogenesis of Krabbe disease.

Hematopoietic Stem Cell Transplantation for Storage Disorders: Present Status

Storage disorders are a group of inborn errors of metabolism caused by the defective activity of lysosomal enzymes or transporters. All of these disorders have multisystem involvement with variable degrees of neurological features. Neurological manifestations are one of the most difficult aspects of treatment concerning these diseases. The available treatment modalities for some of these disorders include enzyme replacement therapy, substrate reduction therapy, hematopoietic stem cell transplantation (HSCT) and the upcoming gene therapies. As a one-time intervention, the economic feasibility of HSCT makes it an attractive option for treating these disorders, especially in lower and middle-income countries. Further, improvements in peri-transplantation medical care, better conditioning regimens and better supportive care have improved the outcomes of patients undergoing HSCT. In this review, we discuss the current evidence for HSCT in various storage disorders and its suitability as a mode of therapy for the developing world.

Chronic Rapamycin administration via drinking water mitigates the pathological phenotype in a Krabbe disease mouse model through autophagy activation

Krabbe disease (KD) is a rare disorder arising from the deficiency of the lysosomal enzyme galactosylceramidase (GALC), leading to the accumulation of the cytotoxic metabolite psychosine (PSY) in the nervous system. This accumulation triggers demyelination and neurodegeneration, and despite ongoing research, the underlying pathogenic mechanisms remain incompletely understood, with no cure currently available. Previous studies from our lab revealed the involvement of autophagy dysfunctions in KD pathogenesis, showcasing p62-tagged protein aggregates in the brains of KD mice and heightened p62 levels in the KD sciatic nerve. We also demonstrated that the autophagy inducer Rapamycin (RAPA) can partially reinstate the wild type (WT) phenotype in KD primary cells by decreasing the number of p62 aggregates. In this study, we tested RAPA in the Twitcher (TWI) mouse, a spontaneous KD mouse model. We administered the drug ad libitum via drinking water (15 mg/L) starting from post-natal day (PND) 21-23. We longitudinally monitored the mouse motor performance through grip strength and rotarod tests, and a set of biochemical parameters related to the KD pathogenesis (i.e. autophagy markers expression, PSY accumulation, astrogliosis and myelination). Our findings demonstrate that RAPA significantly enhances motor functions at specific treatment time points and reduces astrogliosis in TWI brain, spinal cord, and sciatic nerves. Utilizing western blot and immunohistochemistry, we observed a decrease in p62 aggregates in TWI nervous tissues, corroborating our earlier in-vitro results. Moreover, RAPA treatment partially removes PSY in the spinal cord. In conclusion, our results advocate for considering RAPA as a supportive therapy for KD. Notably, as RAPA is already available in pharmaceutical formulations for clinical use, its potential for KD treatment can be rapidly evaluated in clinical trials.

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

OBJECTIVE

This review aimed to synthesize the experiences of patients with metachromatic leukodystrophy, adrenoleukodystrophy, or Krabbe disease and those of their families.

INTRODUCTION

Leukodystrophies are metabolic diseases caused by genetic mutations. There are multiple forms of the disease, varying in age of onset and symptoms. The progression of leukodystrophies worsens central nervous system symptoms and significantly affects the lives of patients and their families.

INCLUSION CRITERIA

Qualitative studies on the experiences of patients with leukodystrophies and their family members were included. These experiences included treatments such as enzyme replacement therapy and hematopoietic stem cell transplantation; effects of tracheostomy and gastrostomy; burdens on the family, coordinating care within the health care system, and family planning due to genetic disorders. This review considered studies in any setting.

METHODS

MEDLINE (Ovid), CINAHL Plus (EBSCOhost), APA PsycINFO (EBSCOhost), Scopus, and MedNar databases were searched on November 18, 2022. Study selection, critical appraisal, data extraction, and data synthesis were conducted in accordance with the JBI methodology for systematic reviews of qualitative evidence, and synthesized findings were evaluated according to the ConQual approach.

RESULTS

Eleven studies were eligible for synthesis, and 45 findings were extracted corresponding with participants' voices. Of these findings, 40 were unequivocal and 5 were credible. The diseases in the included studies were metachromatic leukodystrophy and adrenoleukodystrophy; no studies were identified for patients with Krabbe disease and their families. These findings were grouped into 11 categories and integrated into 3 synthesized findings, including i) providing care by family members and health care providers as physical symptoms progress, which relates to effects of the characteristics of progressive leukodystrophies; ii) building medical teamwork to provide appropriate support services, comprising categories related to the challenges experienced with the health care system for patients with leukodystrophy and their families; and iii) coordinating family functions to accept and cope with the disease, which included categories related to family psychological difficulties and role divisions within the family. According to the ConQual criteria, the second synthesized finding had a low confidence level, and the first and third synthesized findings had a very low confidence level.

CONCLUSIONS

The synthesized findings of this review provide evidence on the experiences of patients with metachromatic leukodystrophy or adrenoleukodystrophy and their families. These findings indicate that there are challenges in managing a patient's physical condition and coordinating the health care system and family functions.

REVIEW REGISTRATION

PROSPERO CRD42022318805.

Clinical feature, GALC variant spectrum, and genotype-phenotype correlation in Korean Krabbe disease patients: Multicenter experience over 13 years

Krabbe disease (KD) is an autosomal recessive neurodegenerative disorder caused by deficiency of the galactocerebrosidase (GALC) due to variants in the GALC gene. Here, we provide the first and the largest comprehensive analysis of clinical and genetic characteristics, and genotype-phenotype correlations of KD in Korean in comparison with other ethnic groups. From June 2010 to June 2023, 10 patients were diagnosed with KD through sequencing of GALC. Clinical features, and results of GALC sequencing, biochemical test, neuroimaging, and neurophysiologic test were obtained from medical records. An additional nine previously reported Korean KD patients were included for review. In Korean KD patients, the median age of onset was 2 years (3 months-34 years) and the most common phenotype was adult-onset (33%, 6/18) KD, followed by infantile KD (28%, 5/18). The most frequent variants were c.683_694delinsCTC (23%) and c.1901T>C (23%), while the 30-kb deletion was absent. Having two heterozygous pathogenic missense variants was associated with later-onset phenotype. Clinical features were similar to those of other ethnic groups. In Korean KD patients, the most common phenotype was the adult-onset type and the GALC variant spectrum was different from that of the Caucasian population. This study would further our understanding of KD.

From pathological mechanisms in Krabbe disease to cutting-edge therapy: A comprehensive review

Since its initial documentation by Knud Krabbe in 1916, numerous studies have scrutinized the characteristics of Krabbe disease (KD) until the identification of the mutation in the GALC gene. In alignment with that, we investigated the natural history of KD spanning eight decades to gain a deeper understanding of the evolutionary trajectory of its mechanisms. Through our comprehensive analysis, we unearthed additional novel elements in molecular biology involving the micropathological mechanism of the disease. This review offers an updated perspective on the metabolic disorder that defines KD. Recently, extracellular vesicles (EVs), autophagy impairment, and α-synuclein have emerged as pivotal players in the neuropathological processes. EVs might serve as a cellular mechanism to avoid or alleviate the detrimental impacts of excessive toxic psychosine levels, and extracting EVs could contribute to synapse dysfunction. Autophagy impairment was found to be independent of psychosine and reliant on AKT and B-cell lymphoma 2. Additionally, α-synuclein has been recognized for inducing cellular death and dysfunction in common biological pathways. Our objective is to assess the effectiveness of advanced therapies in addressing this particular condition. While hematopoietic stem cells have been a primary treatment, its administration proves challenging, particularly in the presymptomatic phase. In this review, we have compiled information from over 10 therapy trials, comparing them based on their benefits and disadvantage.

Leukodystrophy Imaging: Insights for Diagnostic Dilemmas

Leukodystrophies, a group of rare demyelinating disorders, mainly affect the CNS. Clinical presentation of different types of leukodystrophies can be nonspecific, and thus, imaging techniques like MRI can be used for a more definitive diagnosis. These diseases are characterized as cerebral lesions with characteristic demyelinating patterns which can be used as differentiating tools. In this review, we talk about these MRI study findings for each leukodystrophy, associated genetics, blood work that can help in differentiation, emerging diagnostics, and a follow-up imaging strategy. The leukodystrophies discussed in this paper include X-linked adrenoleukodystrophy, metachromatic leukodystrophy, Krabbe's disease, Pelizaeus-Merzbacher disease, Alexander's disease, Canavan disease, and Aicardi-Goutières Syndrome.

Epilepsy in sulfite oxidase deficiency and related disorders: insights from neuroimaging and genetics

Sulfite oxidase deficiency (SOD) and related disorders, especially molybdenum cofactor deficiency (MoCD), are a group of rare and severe neurometabolic disorders caused by gene mutations that affect the sulfur-containing amino acid catabolic pathway. These disorders are characterized by distinctive neuroimaging features such as diffuse cerebral atrophy, multicystic encephalomalacia, and ventriculomegaly in early infancy. These features are essential for early diagnosis and treatment. Moreover, the genetics of these disorders are complex but have been increasingly elucidated in the era of molecular medicine. Therefore, we reviewed 28 articles (published from January 1967 until October 2021) on SOD and MoCD, focusing on their neuroimaging and genetic aspects. We highlighted the differences between SOD and MoCD and other conditions that may mimic them, such as common neonatal hypoxic-ischemic encephalopathy and uncommon neonatal metabolic disorder (Leigh syndrome). We also summarized the current knowledge on the genetic mechanisms and the manifestation of seizure disorders of SOD and MoCD. In conclusion, if clinical, neuroimaging, and neuropathological findings suggest a possible SOD or related disorder; extensive molecular diagnostics should be performed to confirm the diagnosis.

Zebra-Sphinx: Modeling Sphingolipidoses in Zebrafish

Sphingolipidoses are inborn errors of metabolism due to the pathogenic mutation of genes that encode for lysosomal enzymes, transporters, or enzyme cofactors that participate in the sphingolipid catabolism. They represent a subgroup of lysosomal storage diseases characterized by the gradual lysosomal accumulation of the substrate(s) of the defective proteins. The clinical presentation of patients affected by sphingolipid storage disorders ranges from a mild progression for some juvenile- or adult-onset forms to severe/fatal infantile forms. Despite significant therapeutic achievements, novel strategies are required at basic, clinical, and translational levels to improve patient outcomes. On these bases, the development of in vivo models is crucial for a better understanding of the pathogenesis of sphingolipidoses and for the development of efficacious therapeutic strategies. The teleost zebrafish (Danio rerio) has emerged as a useful platform to model several human genetic diseases owing to the high grade of genome conservation between human and zebrafish, combined with precise genome editing and the ease of manipulation. In addition, lipidomic studies have allowed the identification in zebrafish of all of the main classes of lipids present in mammals, supporting the possibility to model diseases of the lipidic metabolism in this animal species with the advantage of using mammalian lipid databases for data processing. This review highlights the use of zebrafish as an innovative model system to gain novel insights into the pathogenesis of sphingolipidoses, with possible implications for the identification of more efficacious therapeutic approaches.

Preclinical studies in Krabbe disease: A model for the investigation of novel combination therapies for lysosomal storage diseases

Krabbe disease (KD) is a lysosomal storage disease (LSD) caused by mutations in the galc gene. There are over 50 monogenetic LSDs, which largely impede the normal development of children and often lead to premature death. At present, there are no cures for LSDs and the available treatments are generally insufficient, short acting, and not without co-morbidities or long-term side effects. The last 30 years have seen significant advances in our understanding of LSD pathology as well as treatment options. Two gene therapy-based clinical trials, NCT04693598 and NCT04771416, for KD were recently started based on those advances. This review will discuss how our knowledge of KD got to where it is today, focusing on preclinical investigations, and how what was discovered may prove beneficial for the treatment of other LSDs.

Lysosomal storage disorders: Clinical and therapeutic aspects

The lysosomal storage disorders are hereditary metabolic disorders characterized by autosomal recessive inheritance, mainly caused by deficiency of an enzyme responsible for the intra-lysosomal breakdown of various substrates and products of cellular metabolism. This chapter examines the underlying defects, clinical manifestations, and provides context for the expected clinical outcome of various available therapy options employing enzyme replacement therapy, hematopoietic stem cell transplantation, substrate reduction, and enzyme enhancement therapies.

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.

Unrelated umbilical cord blood transplantation for children with hereditary leukodystrophy: A retrospective study

Objective

To analyze the efficiency of unrelated umbilical cord blood transplantation (UCBT) in the treatment of hereditary leukodystrophy following busulfan- and cyclophosphamide-based myeloablative chemotherapy.

Methods

A retrospective study was performed in patients with hereditary leukodystrophy who underwent UCBT after myeloablative chemotherapy between April 2015 and March 2020.

Results

The study cohort included 12 pediatric patients (ten males), nine with cerebral adrenoleukodystrophy (ALD) and three with juvenile globoid cell leukodystrophy (GLD). All received HLA-matched or partially mismatched unrelated UCBT. There were no cases of graft rejection. Median neutrophil engraftment time was 20 days [12–33 days] and median platelet engraftment time was 29 days [14–65 days]. Median follow-up was 36 months [1–86 months], and the overall survival rate for patients with cerebral ALD and juvenile GLD after UCBT was 77.8% (7/9) and 100% (3/3), respectively. In patients with ALD, although lipid profiles (serum very-long-chain fatty acid) were improved post-UCBT, six patients demonstrated worse neurologic function score and performance status post-UCBT, and six patients had higher Loes scores at last follow-up compared with baseline. In patients with juvenile GLD, all patients showed stable neurologic function score and performance status despite the Loes score of one patient increased slightly after transplantation.

Conclusion

In patients with cerebral ALD, patients with no or mild neurological symptoms can benefit from UCBT, while UCBT cannot reverse advanced disease. In patients with juvenile GLD, UCBT is safe and contributes to stabilize neurological function.

Newborn Screening Is on a Collision Course with Public Health Ethics

Newborn screening was established over 50 years ago to identify cases of disorders that were serious, urgent, and treatable, mirroring the criteria of Wilson and Jungner. In the last decade, conditions have been added to newborn screening that do not strictly meet these criteria, and genomic newborn screening is beginning to be discussed. Some of these new and proposed additions to newborn screening entail serious public health ethical issues that need to be explored.

A neglected neurodegenerative disease: Adult-onset globoid cell leukodystrophy

Globoid cell leukodystrophy (GLD), or Krabbe disease (KD) is a rare neurodegenerative disease, and adult-onset GLD is more even neglected by clinicians. This review provides detailed discussions of the serum enzymes, genes, clinical manifestations, neuroimaging features, and therapies of GLD, with particular emphasis on the characteristics of adult-onset GLD, in an attempt to provide clinicians with in-depth insights into this disease.

Imaging of Inherited Metabolic and Endocrine Disorders

"Inherited metabolic disorders represent a large group of disorders of which approximately 25% present in neonatal period with acute metabolic decompensation, rapid clinical deterioration, and often nonspecific imaging findings. Neonatal onset signifies the profound severity of the metabolic abnormality compared with cases with later presentation and necessitates rapid diagnosis and urgent therapeutic measures in an attempt to decrease the extent of brain injury and prevent grave neurologic sequela or death. Here, the authors discuss classification and clinical and imaging findings in a spectrum of metabolic and endocrine disorders with neonatal presentation."

Why must the debate continue on Krabbe disease newborn screening?

Since the early 2000s, many families impacted by Krabbe disease have tried to implement newborn screening for this rare fatal neurological disorder in their home state. However, despite grassroots efforts, states have been unable to agree to newborn screening for Krabbe disease due to poor testing mechanisms, lack of understanding of the developmental outcomes of transplantation, low incidence rate, and more. Over the past five years, many organizations and experts have made significant strides to help Krabbe disease meet the eligibility requirements for state panels and the Recommended Uniform Screening Panel (RUSP). Nevertheless, ethicists and newborn screening advisory committees continue to disregard the progress our community has made in the treatment and screening of Krabbe disease.

Benefits of newborn screening and hematopoietic cell transplant in infantile Krabbe disease

Infantile Krabbe disease (IKD) can be treated with hematopoietic cell transplantation (HCT) if done during the first weeks of life before symptoms develop. To facilitate this, newborn screening (NBS) has been instituted in 8 US states. An application to add IKD to the recommended NBS panel is currently under review. In this report, the outcomes of newborns with IKD diagnosed through NBS and treated with HCT are presented. The unique challenges associated with NBS for this disease are discussed, including opportunities for earlier diagnosis and streamlining treatment referrals. This is a retrospective review of six infants with IKD detected by NBS who were referred for HCT. The timing from diagnosis to HCT was examined, and both HCT and neurodevelopmental outcomes are described. Neurologic testing before HCT revealed evidence of active IKD in all infants. All underwent HCT between 24 and 40 days of age, were successfully engrafted, and are alive 30 to 58 months later (median, 47.5 months). All are gaining developmental milestones albeit at a slower pace than unaffected age-matched peers. Gross motor function is most notably affected. NBS for these patients enabled early access to HCT, the only currently available treatment of infants with IKD. All children are alive and have derived developmental and neurologic benefits from timely HCT. Long-term follow up is ongoing. Optimization of HCT and further development of emerging therapies, all of which must be delivered early in life, are expected to further improve outcomes of infants with IKD.

The diagnosis and management of Gaucher disease in pediatric patients: Where do we go from here?

Gaucher disease (GD) is an autosomal recessive inherited lysosomal storage disease that often presents in early childhood and is associated with damage to multiple organ systems. Many challenges associated with GD diagnosis and management arise from the considerable heterogeneity of disease presentations and natural history. Phenotypic classification has traditionally been based on the absence (in type 1 GD) or presence (in types 2 and 3 GD) of neurological involvement of varying severity. However, patient management and prediction of prognosis may be best served by a dynamic, evolving definition of individual phenotype rather than by a rigid system of classification. Patients may experience considerable delays in diagnosis, which can potentially be reduced by effective screening programs; however, program implementation can involve ethical and practical challenges. Variation in the clinical course of GD and an uncertain prognosis also complicate decisions concerning treatment initiation, with differing stakeholder perspectives around efficacy and acceptable cost/benefit ratio. We review the challenges faced by physicians in the diagnosis and management of GD in pediatric patients. We also consider future directions and goals, including acceleration of accurate diagnosis, improvements in the understanding of disease heterogeneity (natural history, response to treatment, and prognosis), the need for new treatments to address unmet needs for all forms of GD, and refinement of the tools for monitoring disease progression and treatment efficacy, such as specific biomarkers.

European Academy of Neurology guidance for developing and reporting clinical practice guidelines on rare neurological diseases

BACKGROUND AND PURPOSE

Rare diseases affect up to 29 million people in the European Union, and almost 50% of them affect the nervous system or muscles. Delays in diagnosis and treatment onset and insufficient treatment choices are common. Clinical practice guidelines (CPGs) may improve the diagnosis and treatment of patients and optimize care pathways, delivering the best scientific evidence to all clinicians treating these patients. Recommendations are set for developing and reporting high-quality CPGs on rare neurological diseases (RNDs) within the European Academy of Neurology (EAN), through a consensus procedure.

METHODS

A group of 27 experts generated an initial list of items that were evaluated through a two-step Delphi consensus procedure and a face-to-face meeting. The final list of items was reviewed by an external review group of 58 members.

RESULTS

The consensus procedure yielded 63 final items. Items are listed according to the domains of the AGREE instruments and concern scope and purpose, stakeholder involvement, rigour of development, and applicability. Additional items consider reporting and ethical issues. Recommendations are supported by practical examples derived from published guidelines and are presented in two tables: (1) items specific to RND CPGs, and general guideline items of special importance for RNDs, or often neglected; (2) items for guideline development within the EAN.

CONCLUSIONS

This guidance aims to provide solutions to the issues specific to RNDs. This consensus document, produced by many experts in various fields, is considered to serve as a starting point for further harmonization and for increasing the quality of CPGs in the field of RNDs.

Efficacy and Safety of a Krabbe Disease Gene Therapy

Krabbe disease is a lysosomal storage disease caused by mutations in the gene that encodes galactosylceramidase, in which galactosylsphingosine (psychosine) accumulation drives demyelination in the central and peripheral nervous systems, ultimately progressing to death in early childhood. Gene therapy, alone or in combination with transplant, has been developed for almost two decades in mouse models, with increasing therapeutic benefit paralleling the improvement of next-generation adeno-associated virus (AAV) vectors. This effort has recently shown remarkable efficacy in the canine model of the disease by two different groups that used either systemic or cerebrospinal fluid (CSF) administration of AAVrh10 or AAV9. Building on our experience developing CSF-delivered, AAV-based drug products for a variety of neurodegenerative disorders, we conducted efficacy, pharmacology, and safety studies of AAVhu68 delivered to the CSF in two relevant natural Krabbe animal models, and in nonhuman primates. In newborn Twitcher mice, the highest dose (1 × 10¹¹ genome copies [GC]) of AAVhu68.hGALC injected into the lateral ventricle led to a median survival of 130 days compared to 40.5 days in vehicle-treated mice. When this dose was administered intravenously, the median survival was 49 days. A single intracisterna magna injection of AAVhu68.cGALC at 3 × 10¹³ GC into presymptomatic Krabbe dogs increased survival for up to 85 weeks compared to 12 weeks in controls. It prevented psychosine accumulation in the CSF, preserved peripheral nerve myelination, ambulation, and decreased brain neuroinflammation and demyelination, although some regions remained abnormal. In a Good Laboratory Practice-compliant toxicology study, we administered the clinical candidate into the cisterna magna of 18 juvenile rhesus macaques at 3 doses that displayed efficacy in mice. We observed no dose-limiting toxicity and sporadic minimal degeneration of dorsal root ganglia (DRG) neurons. Our studies demonstrate the efficacy, scalability, and safety of a single cisterna magna AAVhu68 administration to treat Krabbe disease. ClinicalTrials.Gov ID: NCT04771416.

Hospitalization Burden and Incidence of Krabbe Disease

OBJECTIVE

The purpose of our study was to understand the healthcare burden and incidence of Krabbe disease (Krabbe).

METHODS

Retrospective analysis of Krabbe patients identified October 1, 2015 through December 31, 2020, ages birth through age 3, evaluated in two national databases. We estimated point prevalence and incidence from year 2016 data.

RESULTS

We identified 98 unique Krabbe patients with 736 visits including 260 were inpatient admissions. Total healthcare charges were $51.5 million dollars. We determined a point prevalence of 34 68 Krabbe patients in 2016 ages 0 3 years. This estimates a birth incidence of ~1 in 310,000 live births. Significance: Krabbe disease patients had over $51 million in health care charges and hundreds of hospitalizations. Estimated prevalence and birth incidence is similar to rates observed from newborn screening. Our findings show the tremendous health impacts of Krabbe disease, and provide guidance for efforts in screening and treatment planning.

Krabbe Disease: Prospects of Finding a Cure Using AAV Gene Therapy

Krabbe Disease (KD) is an autosomal metabolic disorder that affects both the central and peripheral nervous systems. It is caused by a functional deficiency of the lysosomal enzyme, galactocerebrosidase (GALC), resulting in an accumulation of the toxic metabolite, psychosine. Psychosine accumulation affects many different cellular pathways, leading to severe demyelination. Although there is currently no effective therapy for Krabbe disease, recent gene therapy-based approaches in animal models have indicated a promising outlook for clinical treatment. This review highlights recent findings in the pathogenesis of Krabbe disease, and evaluates AAV-based gene therapy as a promising strategy for treating this devastating pediatric disease.

National U.S. Patient and Transplant Data for Krabbe Disease

Krabbe disease (KD) is a leukodystrophy caused by mutations in the galactosylceramidase gene. Presymptomatic hematopoietic stem cell transplantation (HSCT) is associated with improved outcomes, but most data are from single-center studies. Our objective was to characterize national patterns of HSCT for KD including whether there were disparities in HSCT utilization and outcomes. We conducted a retrospective study of KD patients ≤ age 18 years from November 1, 2015, through December 31, 2019, using the U.S. Children's Hospital Association's Pediatric Health Information System database. We evaluated outcomes for HSCT, intensive care unit days, and mortality, comparing age, sex, race/ethnicity, rural/urban location, and median household income. We identified 91 KD patients. HSCT, performed in 32% of patients, was associated with reduced mortality, 31 vs. 68% without HSCT (p < 0.003). Trends included the fact that more males than females had HSCT (39 vs. 23%); more Asian and White patients had HSCT compared to Black or Hispanic patients (75, 33, 25, and 17%, respectively); and patients from households with the lowest-income quartile (< $25,000) had more HSCT compared to higher-income quartiles (44 vs. 33, 30, and 0%). Overall, receiving HSCT was associated with reduced mortality. We noted trends in patient groups who received HSCT. Our findings suggest that disparities in receiving HSCT could affect outcomes for KD patients.

Current and Future Prospects for Gene Therapy for Rare Genetic Diseases Affecting the Brain and Spinal Cord

In recent years, gene therapy has been raising hopes toward viable treatment strategies for rare genetic diseases for which there has been almost exclusively supportive treatment. We here review this progress at the pre-clinical and clinical trial levels as well as market approvals within diseases that specifically affect the brain and spinal cord, including degenerative, developmental, lysosomal storage, and metabolic disorders. The field reached an unprecedented milestone when Zolgensma® (onasemnogene abeparvovec) was approved by the FDA and EMA for in vivo adeno-associated virus-mediated gene replacement therapy for spinal muscular atrophy. Shortly after EMA approved Libmeldy®, an ex vivo gene therapy with lentivirus vector-transduced autologous CD34-positive stem cells, for treatment of metachromatic leukodystrophy. These successes could be the first of many more new gene therapies in development that mostly target loss-of-function mutation diseases with gene replacement (e.g., Batten disease, mucopolysaccharidoses, gangliosidoses) or, less frequently, gain-of-toxic-function mutation diseases by gene therapeutic silencing of pathologic genes (e.g., amyotrophic lateral sclerosis, Huntington's disease). In addition, the use of genome editing as a gene therapy is being explored for some diseases, but this has so far only reached clinical testing in the treatment of mucopolysaccharidoses. Based on the large number of planned, ongoing, and completed clinical trials for rare genetic central nervous system diseases, it can be expected that several novel gene therapies will be approved and become available within the near future. Essential for this to happen is the in depth characterization of short- and long-term effects, safety aspects, and pharmacodynamics of the applied gene therapy platforms.

Newborn screening system: Safety, technology, advocacy

Newborn screening (NBS) is more than 50 years old and has proven to be a powerful and successful public health system. NBS must be regarded as a system and not simply as a test. We need to work as a community to improve the culture of safety for the NBS system and thereby to reduce the risk of babies being missed by the NBS system. Adding new technologies will not prevent system failures; that will require adherence to the culture of safety. Some have argued that every newborn should have their genome sequenced at birth and this sequencing could be part of NBS. However, NBS has depended on biomarker phenotypes throughout its history and our understanding of the relationships between genotype and phenotype is imperfect. Therefore, we should avoid being seduced by genomic sequencing technology and continue to focus on phenotypic biomarkers in NBS.

Leukodystrophies in Children: Diagnosis, Care, and Treatment

Leukodystrophies are a group of genetically determined disorders that affect development or maintenance of central nervous system myelin. Leukodystrophies have an incidence of at least 1 in 4700 live births and significant morbidity and elevated risk of early death. This report includes a discussion of the types of leukodystrophies; their prevalence, clinical presentation, symptoms, and diagnosis; and current and future treatments. Leukodystrophies can present at any age from infancy to adulthood, with variability in disease progression and clinical presentation, ranging from developmental delay to seizures to spasticity. Diagnosis is based on a combination of history, examination, and radiologic and laboratory findings, including genetic testing. Although there are few cures, there are significant opportunities for care and improvements in patient well-being. Rapid advances in imaging and diagnosis, the emergence of and requirement for timely treatments, and the addition of leukodystrophy screening to newborn screening, make an understanding of the leukodystrophies necessary for pediatricians and other care providers for children.

Low Psychosine in Krabbe Disease with Onset in Late Infancy: A Case Report

Krabbe disease (KD) is a rare inherited neurodegenerative disorder caused by a deficiency in galactocerebrosidase enzyme activity, which can present in early infancy, requiring an urgent referral for hematopoietic stem cell transplantation, or later in life. Newborn screening (NBS) for KD requires identification and risk-stratification of patients based on laboratory values to predict disease onset in early infancy or later in life. The biomarker psychosine plays a key role in NBS algorithms to ascertain probability of early-onset disease. This report describes a patient who was screened positive for KD in New York State, had a likely pathogenic genotype, and showed markedly reduced enzyme activity but surprisingly low psychosine levels. The patient ultimately developed KD in late infancy, an outcome not clearly predicted by existing NBS algorithms. It remains critical that psychosine levels be evaluated alongside genotype, enzyme activity levels, and the patient's evolving clinical presentation, ideally in consultation with experts in KD, in order to guide diagnosis and plans for monitoring.

Newborn Screening for Krabbe Disease-Illinois Experience: Role of Psychosine in Diagnosis of the Disease

Population-based newborn screening for Krabbe disease was initiated by measurement of galactocerebrosidase (GALC) activity in the state of Illinois in December 2017. Due to the poor specificity of GALC for the diagnosis of Krabbe disease, second-tier testing services were provided to reduce the false positive rates for disease monitoring. Using ultra-pressure liquid chromatography coupled to mass spectrometry assay, a total of 497,147 newborns were screened. In total, 288 infants' specimens (0.06%) having reduced GALC activity were sent out for second-tier testing to a reference laboratory. All newborns' reduced GALC specimens were tested for psychosine levels, the presence of a 30-kb deletion and GALC sequencing. The results showed that two infants had elevated psychosine levels (10 and 35 nM) and were referred immediately for evaluation and treatment for Infantile Krabbe disease, and six infants had intermediate PSY levels (≥2 to 5 nM) and are under observation as suspected candidates for late-onset Krabbe disease. In addition, 178 infants had pseudodeficiency alleles, all having psychosine levels < 2.0 nM. Our data show that a high percentage of reduced GALC activity (62%) was due to the presence of pseudodeficiency alleles in the GALC gene. In conclusion, incorporation of psychosine measurements can identify infants with infantile Krabbe disease and probable late-onset Krabbe infants. Furthermore, Krabbe disease screening can be achieved at public health laboratories, and infants with infantile Krabbe disease can be diagnosed in timely manner for better outcome.

Galactose in human metabolism, glycosylation and congenital metabolic diseases: Time for a closer look

Galactose is an essential carbohydrate for cellular metabolism, as it contributes to energy production and storage in several human tissues while also being a precursor for glycosylation. Galactosylated glycoconjugates, such as glycoproteins, keratan sulfate-containing proteoglycans and glycolipids, exert a plethora of biological functions, including structural support, cellular adhesion, intracellular signaling and many more. The biological relevance of galactose is further entailed by the number of pathogenic conditions consequent to defects in galactosylation and galactose homeostasis. The growing number of rare congenital disorders involving galactose along with its recent therapeutical applications are drawing increasing attention to galactose metabolism. In this review, we aim to draw a comprehensive overview of the biological functions of galactose in human cells, including its metabolism and its role in glycosylation, and to provide a systematic description of all known congenital metabolic disorders resulting from alterations of its homeostasis.

Recent Advancements in the Diagnosis and Treatment of Leukodystrophies

Leukodystrophies and genetic leukoencephalopathies comprise a growing group of inherited white matter disorders. Diagnostic rates have improved with increased utilization of next generation sequencing. As treatment options continue to advance for leukodystrophies, so will candidacy for inclusion in the United States' newborn Recommended Universal Screening Panel as was achieved for X-linked adrenoleukodystrophy. Stem cell therapies have become standard of care for selected leukodystrophies. However, transplantation-related risks remain high and outcomes are not fully satisfactory. Transduction of autologous hematopoietic stem cells with lentiviral vectors, referred to as ex vivo gene therapy, circumvents some, but not all, of the risks of traditional transplantation and has recently been demonstrated to be safe and efficective in clinical studies of X-linked adrenoleukodystrophy and metachromatic leukodystrophy. Gene therapy, through direct infusion of adeno-associated virus vectors, has emerged as a safer alternative for many monogenetic pediatric neurological disorders. Numerous preclinical studies have shown safety and efficacy of adeno-associated virus gene therapy in leukodystrophies allowing expanded access treatment for Canavan disease prior to initiation of a clinical trial. For inherited white matter disorders resulting from overexpression of a protein, such as Pelizaeus-Merzbacher disease, emerging RNA therapies have shown success in preclinical studies and promise for rapid translation to the clinic. Lastly, small molecule and protein therapies remain a long-term treatment option for a number of leukodystrophies, including intrathecal enzyme replacement therapy for metachromatic leukodystrophy. Herein we review recent advances in diagnosis and treatment of inherited white matter disorders.

Substrate Reduction Therapy for Krabbe Disease: Exploring the Repurposing of the Antibiotic D-Cycloserine

Krabbe disease is a lysosomal storage disease that is caused by a deficiency in galactosylceramidase. Infantile onset disease is the most common presentation, which includes progressive neurological deterioration with corresponding demyelination, development of globoid cells, astrocyte gliosis, etc. Hemopoietic stem cell transplantation (HSCT) is a disease modifying therapy, but this intervention is insufficient with many patients still experiencing developmental delays and progressive deterioration. Preclinical studies have used animal models, e.g., twitcher mice, to test different experimental therapies resulting in developments that have led to progressive improvements in the therapeutic impact. Some recent advances have been in the areas of gene therapy and substrate reduction therapy (SRT), as well as using these in combination with HSCT. Unfortunately, new experimental approaches have encountered obstacles which have impeded the translation of novel therapies to human patients. In an effort to identify a safe adjunct therapy, D-cycloserine was tested in preliminary studies in twitcher mice. When administered as a standalone therapy, D-cycloserine was shown to lengthen the lifespan of twitcher mice in a small but significant manner. D-Cycloserine is an FDA approved antibiotic used for drug resistant tuberculosis. It also acts as a partial agonist of the NMDA receptor, which has led to numerous human studies for a range of neuropsychiatric and neurological conditions. In addition, D-cycloserine may inhibit serine palmitoyltransferase (SPT), which catalyzes the rate-limiting step in sphingolipid production. The enantiomer, L-cycloserine, is a much more potent inhibitor of SPT than D-cycloserine. Previously, L-cycloserine was found to act as an effective SRT agent in twitcher mice as both a standalone therapy and as part of combination therapies. L-Cycloserine is not approved for human use, and its potent inhibitory properties may limit its ability to maintain a level of partial inactivation of SPT that is also safe. In theory, D-cycloserine would encompass a much broader dosage range to achieve a safe degree of partial inhibition of SPT, which increases the likelihood it could advance to human studies in patients with Krabbe disease. Furthermore, additional properties of D-cycloserine raise the possibility of other therapeutic mechanisms that could be exploited for the treatment of this disease.

CNS-Targeting Therapies for Lysosomal Storage Diseases: Current Advances and Challenges

During the past decades, several therapeutic approaches have been developed and made rapidly available for many patients afflicted with lysosomal storage disorders (LSDs), inborn organelle disorders with broad clinical manifestations secondary to the progressive accumulation of undegraded macromolecules within lysosomes. These conditions are individually rare, but, collectively, their incidence ranges from 1 in 2,315 to 7,700 live-births. Most LSDs are manifested by neurological symptoms or signs, including developmental delay, seizures, acroparesthesia, motor weakness, and extrapyramidal signs. The chronic and later-onset clinical forms are at one end of the continuum spectrum and are characterized by a subtle and slow progression of neurological symptoms. Due to its inherent physiological properties, unfortunately, the blood-brain barrier (BBB) constitutes a significant obstacle for current and upcoming therapies to achieve the central nervous system (CNS) and treat neurological problems so prevalent in these conditions. To circumvent this limitation, several strategies have been developed to make the therapeutic agent achieve the CNS. This narrative will provide an overview of current therapeutic strategies under development to permeate the BBB, and address and unmet need for treatment of the progressive neurological manifestations, which are so prevalent in these inherited lysosomal disorders.

Family Attitudes regarding Newborn Screening for Krabbe Disease: Results from a Survey of Leukodystrophy Registries

Newborn screening (NBS) for Krabbe disease (KD) is currently underway in eight states in the USA, and there is continued discussion of whether to implement KD NBS in additional states. Workgroup members sought to survey a large number of families affected by KD. Families in KD and leukodystrophy family registries were contacted to seek their participation in The Krabbe Newborn Screening-Family Perspective Survey. The 170 respondents are comprised of the following: 138 family members with a KD individual diagnosed after development of symptoms, 20 notified about KD via NBS, and 12 with a KD individual diagnosed through family history of KD. The key results are that all NBS families with an early-infantile KD family member elected to pursue hematopoietic stem cell transplantation therapy. Of the 170 responders, 165 supported the implementation of KD NBS in all states in the USA.

Impairment of Proteasome and Autophagy Underlying the Pathogenesis of Leukodystrophy

Impairment of the ubiquitin-proteasome-system (UPS) and autophagy causing cytoplasmic aggregation of ubiquitin andp62 have been implicated in the pathogenesis of most neurodegenerative disorders, yet, they have not been fully elucidated in leukodystrophies. The relationship among impairment of UPS, autophagy, and globoid cell leukodystrophy (GLD), one of the most common demyelinating leukodystrophies, is clarified in this study. We examined the ubiquitin and autophagy markers in the brains of twitcher mice, a murine model of infantile GLD, and in human oligodendrocytes incubated with psychosine. Immunohistochemical examinations showed spatiotemporal accumulation of ubiquitin- and p62-aggregates mainly in the white matter of brain and spinal cord at disease progression. Western blot analysis demonstrated a significant accumulation of ubiquitin, p62, and LC3-II in insoluble fraction in parallel with progressive demyelination and neuroinflammation in twitcher brains. In vitro study validated a dose- and time-dependent cytotoxicity of psychosine upon autophagy and UPS machinery. Inhibition of autophagy and UPS exacerbated the accumulation of insoluble ubiquitin, p62, and LC3-II proteins mediated by psychosine cytotoxicity as well as increased cytoplasmic deposition of ubiquitin- and p62-aggregates, and accumulation of autophagosomes and autolysosomes. Further, the subsequent accumulation of reactive oxygen species and reduction of mitochondrial respiration led to cell death. Our studies validate the impairment of proteasome and autophagy underlying the pathogenesis of GLD. These findings provide a novel insight into pathogenesis of GLD and suggest a specific pathomechanism as an ideal target for therapeutic approaches.

Diagnosis of Mucopolysaccharidoses

The mucopolysaccharidoses (MPSs) include 11 different conditions caused by specific enzyme deficiencies in the degradation pathway of glycosaminoglycans (GAGs). Although most MPS types present increased levels of GAGs in tissues, including blood and urine, diagnosis is challenging as specific enzyme assays are needed for the correct diagnosis. Enzyme assays are usually performed in blood, with some samples (as leukocytes) providing a final diagnosis, while others (such as dried blood spots) still being considered as screening methods. The identification of variants in the specific genes that encode each MPS-related enzyme is helpful for diagnosis confirmation (when needed), carrier detection, genetic counseling, prenatal diagnosis (preferably in combination with enzyme assays) and phenotype prediction. Although the usual diagnostic flow in high-risk patients starts with the measurement of urinary GAGs, it continues with specific enzyme assays and is completed with mutation identification; there is a growing trend to have genotype-based investigations performed at the beginning of the investigation. In such cases, confirmation of pathogenicity of the variants identified should be confirmed by measurement of enzyme activity and/or identification and/or quantification of GAG species. As there is a growing number of countries performing newborn screening for MPS diseases, the investigation of a low enzyme activity by the measurement of GAG species concentration and identification of gene mutations in the same DBS sample is recommended before the suspicion of MPS is taken to the family. With specific therapies already available for most MPS patients, and with clinical trials in progress for many conditions, the specific diagnosis of MPS as early as possible is becoming increasingly necessary. In this review, we describe traditional and the most up to date diagnostic methods for mucopolysaccharidoses.

The critical role of psychosine in screening, diagnosis, and monitoring of Krabbe disease

PURPOSE

Newborn screening (NBS) for Krabbe disease (KD) is performed by measurement of galactocerebrosidase (GALC) activity as the primary test. This revealed that GALC activity has poor specificity for KD. Psychosine (PSY) was proposed as a disease marker useful to reduce the false positive rate for NBS and for disease monitoring. We report a highly sensitive PSY assay that allows identification of KD patients with minimal PSY elevations.

METHODS

PSY was extracted from dried blood spots or erythrocytes with methanol containing d₅-PSY as internal standard, and measured by liquid chromatography-tandem mass spectrometry.

RESULTS

Analysis of PSY in samples from controls (N = 209), GALC pseudodeficiency carriers (N = 55), GALC pathogenic variant carriers (N = 27), patients with infantile KD (N = 26), and patients with late-onset KD (N = 11) allowed for the development of an effective laboratory screening and diagnostic algorithm. Additional longitudinal measurements were used to track therapeutic efficacy of hematopoietic stem cell transplantion (HSCT).

CONCLUSION

This study supports PSY quantitation as a critical component of NBS for KD. It helps to differentiate infantile from later onset KD variants, as well as from GALC variant and pseudodeficiency carriers. Additionally, this study provides further data that PSY measurement can be useful to monitor KD progression before and after treatment.

Rare Saposin A deficiency: Novel variant and psychosine analysis

Saposin A is a post-translation product of the prosaposin (PSAP) gene that serves as an activator protein of the galactocerebrosidase (GALC) enzyme, and is necessary for the degradation of certain glycosphingolipids. Deficiency of saposin A leads to a clinical picture identical to that of early-infantile Krabbe disease caused by GALC enzyme deficiency. Galactosylsphingosine, also known as psychosine, is a substrate of the GALC enzyme that is known to be elevated in classic Krabbe disease. We present the case of an 18-month-old male with clinical and radiological findings concerning for Krabbe disease who had preserved GALC enzyme activity and negative GALC gene sequencing, but was found to have a homozygous variant, c.257 T > A (p.I86N), in the saposin A peptide of PSAP. Psychosine determination on dried blood spot at 18 months of age was elevated to 12 nmol/L (normal <3 nmol/L). We present this case to add to the literature on the rare diagnosis of atypical Krabbe disease due to saposin A deficiency, to report a novel presumed pathogenic variant within PSAP, and to suggest that individuals with saposin A deficiency may have elevated levels of psychosine, similar to children with classic Krabbe disease due to GALC deficiency.

Ethical issues with testing and treatment for Krabbe disease

Early-infantile Krabbe disease (EIKD) is an autosomal recessive, progressive, neurodegenerative disorder that usually leads to death in infancy. A study published in 2005 indicated that hematopoietic stem-cell transplantation (HSCT) was effective in the treatment for EIKD when used before the onset of symptoms. This finding suggested that newborn screening for EIKD, which would allow earlier diagnosis, might lead to earlier treatment and better outcomes. In 2006, New York was the first state to implement newborn screening for Krabbe disease; however, the results were not as good as proponents had hoped. In this paper, we present the history of efforts to diagnose and treat EIKD. Based on our findings, we question the efficacy of newborn screening for Krabbe disease. We present two arguments. First, testing itself is too imprecise. Even with the most rigorous testing standards, such as those used in New York, many of the children who are identified as being 'at risk' for EIKD remain asymptomatic. It is unclear if they will remain asymptomatic forever and, thus, whether the tests should be considered 'false positives', or whether they will eventually develop the disease. Second, we question the efficacy of early HSCT. We recommend placing a moratorium on mandatory newborn screening for EIKD. WHAT THIS PAPER ADDS: Current tests to identify which children are likely to develop Krabbe diseased are inadequate. Many children identified as being 'at risk' for early infantile Krabbe disease remain asymptomatic. Psychosine appears to be more specific than low galactosylceramidase levels for diagnosing early infantile Krabbe disease.

Next generation sequencing as second-tier test in high-throughput newborn screening for nephropathic cystinosis

Nephropathic cystinosis is a rare autosomal recessive lysosomal storage disorder, which causes loss of renal proximal tubular function and progressive loss of glomerular function, finally leading to end stage renal failure at school age. In the course of the disease most patients will need kidney transplantation if treatment has not been started before clinical manifestation. With an effective treatment available, a newborn screening assay is highly demanded. Since newborns with cystinosis usually do not show symptoms within the first months of life and no biochemical markers are easily detectable, a DNA-based method seems to be an obvious tool for early diagnosis. Screening was performed using high-throughput nucleic acid extraction followed by 384-well qPCR and melting analysis for the three most frequent variants (57 kb deletion NC_000017.11:g.3600934_3658165del (GRCh38); c.18_21del GACT; c.926dupG) responsible for the defective lysosomal membrane protein cystinosin (CTNS). To increase sensitivity, all heterozygous samples identified in qPCR assay were verified and screened for additional variants by applying next generation sequencing. From January 2018 to July 2019 nearly 292,000 newborns were successfully screened. We identified two newborns with a homozygous 57 kb deletion and a second one with heterozygous 57 kb deletion and a G>C substitution at position c.-512 on the second allele. Cystinosis is an example for diseases caused by a limited number of high prevalence and a high number of low prevalence variants. We have shown that qPCR combined with NGS can be used as a high throughput, cost effective tool in newborn screening for such diseases.

Hematopoietic Stem Cell Transplantation to Treat Leukodystrophies: Clinical Practice Guidelines from the Hunter's Hope Leukodystrophy Care Network

The leukodystrophies are a heterogeneous group of inherited diseases characterized by progressive demyelination of the central nervous system leading to devastating neurologic symptoms and premature death. Hematopoietic stem cell transplantation (HSCT) has been successfully used to treat certain leukodystrophies, including adrenoleukodystrophy, globoid leukodystrophy (Krabbe disease), and metachromatic leukodystrophy, over the past 30 years. To date, these complex patients have primarily been transplanted at a limited number of pediatric centers. As the number of cases identified through pregnancy and newborn screening is increasing, additional centers will be required to treat these children. Hunter's Hope created the Leukodystrophy Care Network in part to create and standardize high-quality clinical practice guidelines to guide the care of affected patients. In this report the clinical guidelines for the care of pediatric patients with leukodystrophies undergoing treatment with HSCT are presented. The initial transplant evaluation, determination of patient eligibility, donor selection, conditioning, supportive care, and post-transplant follow-up are discussed. Throughout these guidelines the need for early detection and treatment and the role of the partnership between families and multidisciplinary providers are emphasized.

Hematopoietic Stem Cell Transplantation: A Neonatal Perspective

Allogeneic hematopoietic stem cell transplantation (HSCT) is indicated in various nonmalignant disorders that arise from genetic, hematopoietic, and immune system defects. Many of the disorders described here have life-threatening consequences in the absence of HSCT, a curative intervention. However, timing and approach to HSCT vary by disorder and optimum results are achieved by performing transplantation before irreversible disease-related morbidity or infectious complications. This article details the principles of HSCT in the very young, lists indications, and explores the factors that contribute to successful outcomes based on transplantation and disease-related nuances. It provides an overview into the HSCT realm from a neonatologist's perspective, describes the current status of transplantation for relevant disorders of infancy, and provides a glimpse into future efforts at improving on current success.

Early progression of Krabbe disease in patients with symptom onset between 0 and 5 months

BACKGROUND

Krabbe disease is a rare neurological disorder caused by a deficiency in the lysosomal enzyme, β-galactocerebrosidase, resulting in demyelination of the central and peripheral nervous systems. If left without treatment, Krabbe disease results in progressive neurodegeneration with reduced quality of life and early death. The purpose of this prospective study was to describe the natural progression of early onset Krabbe disease in a large cohort of patients.

METHODS

Patients with early onset Krabbe disease were prospectively evaluated between 1999 and 2018. Data sources included diagnostic testing, parent questionnaires, standardized multidisciplinary neurodevelopmental assessments, and neuroradiological and neurophysiological tests.

RESULTS

We evaluated 88 children with onset between 0 and 5 months. Median age of symptom onset was 4 months; median time to diagnosis after onset was 3 months. The most common initial symptoms were irritability, feeding difficulties, appendicular spasticity, and developmental delay. Other prevalent symptoms included axial hypotonia, abnormal deep tendon reflexes, constipation, abnormal pupillary response, scoliosis, loss of head control, and dysautonomia. Results of nerve conduction studies showed that 100% of patients developed peripheral neuropathy by 6 months of age. Median galactocerebrosidase enzyme activity was 0.05 nmol/h/mg protein. The median survival was 2 years.

CONCLUSIONS

This is the largest prospective natural history study of Krabbe disease. It provides a comprehensive description of the disease during the first 2 years of life. With recent inclusion of state mandated newborn screening programs and promising therapeutic interventions, enhancing our understanding of disease progression in early onset Krabbe disease will be critical for developing treatments, designing clinical trials, and evaluating outcomes.

Current Therapeutic Approaches in Leukodystrophies: A Review

Leukodystrophies are a heterogeneous class of genetic diseases affecting the white matter in the central nervous system with a broad range of clinical manifestations and a frequently progressive course. An interest in precision medicine has emerged over the last several decades, and biomedical research in leukodystrophies has made exciting advances along this front through therapeutic target discovery and novel disease model systems. In this review, we discuss current and emerging therapeutic approaches in leukodystrophies, including gene therapy, antisense oligonucleotide therapy, CRISPR/CAS-based gene editing, and cell and stem cell based therapies.