The effects of early and late bone marrow transplantation in siblings with alpha-mannosidosis. Is early haematopoietic cell transplantation the preferred treatment option?

α-Mannosidosis - An underdiagnosed lysosomal storage disease in individuals with an 'MPS-like' phenotype

Individuals affected by alpha-Mannosidosis suffer from similar clinical symptoms such as respiratory infections, skeletal changes as patients with mucopolysaccharidoses (MPS). α-Mannosidosis is considered as an ultra-rare disorders and also diagnostic testing is often limited. With the availability of novel therapies and easy-to-access diagnostic tests (e.g. Tandem mass spectrometry) using dried blood spots for both enzymatic and genetic testing, the chance for the development of a better understanding of disease and awareness may be triggered. In a pilot study, we have investigated 1010 residual dried blood spot samples from individuals suspicious to MPS. In these study cohort, 158/1010 individuals were genetically confirmed for MPS. Additional biochemical and genetic confirmatory testing for α-mannosidases revealed four individuals with a final diagnosis of α-mannosidosis. This unexpected high number of individuals with α-mannosidosis demonstrated the urgent need of taking this rare disorder in clinical and diagnostic consideration particularly in patients suspicious to MPS.

Use of the Bruininks-Oseretsky test of motor proficiency (BOT-2) to assess efficacy of velmanase alfa as enzyme therapy for alpha-mannosidosis

Objectives

Alpha-mannosidosis is a rare autosomal recessive lysosomal storage disorder resulting from deficient lysosomal alpha-mannosidase activity. Clinical manifestations include progressive balance disorders, immune deficiency, skeletal abnormalities and cognitive deficits beginning in early childhood. Enzyme replacement therapy with recombinant human alpha-mannosidase (velmanase alfa) is scheduled for clinical development in the US beginning in 2020 and has been approved in the EU for treatment of non-neurological manifestations in cases of mild to moderate disease. This study assessed effects of velmanase alfa on fine and gross motor proficiency in children and adults.

Methods

Integrated Bruininks-Oseretsky (BOT-2) test of Motor Proficiency data from velmanase alfa clinical trials was stratified by age for 14 adults and 19 children treated for up to 4 years.

Results

Patients showed global developmental delays at baseline. For the combined adult and pediatric group there was a statistically significant increase (improvement) in BOT-2 total point score of 13% (p = .035, 95% CI 1.0, 25.0) from baseline to last observation. When stratified by pediatric versus adult patients, there was improvement in BOT-2 total point score in patients <18 years (mean percent increase from baseline to last observation 23%) compared to adults (mean decrease of −0.7%). Subtest analysis of individual BOT-2 items captured some improvement following velmanase alfa treatment in pediatric patients.

Conclusions

There was limited ability to assess the BOT-2 change responses in adults. Pediatric patients showed stability or improvement in scaled scores relative to healthy peers, indicating continued skill acquisition, which may increase independence and contribute to improved patient quality of life.

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Alpha-mannosidosis patients have global developmental delay, requiring assistance with many activities of daily living.

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BOT-2 is used to assess improvements in functional capacity in children and young adults.

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Pediatric patients showed stability or improvement in BOT-2 scaled scores relative to healthy peers, indicating continued skill acquisition.

Tandem mass spectrometry-based multiplex assays for α-mannosidosis and fucosidosis

Multiplex tandem mass spectrometry (MS/MS)-based enzyme activity assays for newborn screening (NBS) and diagnosis of lysosomal storage diseases (LSDs) in newborns, using dried blood spots (DBS) on newborn screening cards, have garnered much attention due to its sensitivity, high precision, and the capability to screen for an unprecedented number of diseases in a single assay. Herein we report the development of MS/MS-based enzyme assays for the diagnosis of α-mannosidosis and fucosidosis. These new protocols are able to distinguish untreated patients from random newborns, carriers and a post-bone marrow transplant patient. We have successfully multiplexed the α-mannosidosis assay with a multiplex MS/MS assay for the screening and diagnosis of other LSDs, namely Fabry, Pompe, MPS I, Gaucher, Niemann-Pick-A/B, and Krabbe diseases. Additionally, we also multiplexed the fucosidosis NBS assay with a 5-plex assay that tests for MPS-II, MPS-IIIB, MPS-IVA, MPS-VI and MPS-VII.

Disease progression of alpha-mannosidosis and impact on patients and carers - A UK natural history survey

Introduction

Alpha-mannosidosis is an ultra-rare lysosomal storage disorder resulting from the deficient activity of lysosomal alpha-mannosidase. Alpha-mannosidosis presents as a highly heterogenous condition with large variations in symptom severity and disease progression rates. Quantitative and qualitative data for alpha-mannosidosis patients and their caregivers provide important insights into their daily experiences.

Methods

A survey of nine alpha-mannosidosis patients was carried out in the UK between August 2017 and January 2018. Patient demographics, health-related quality of life (HRQoL), and qualitative data from patients and carers relating to clinical characteristics and impact of the disease and treatment were analysed.

Results

At the time of survey completion, patient age ranged from 7 to 37 years. Five patients were described as 'walking unassisted', one as 'walking with assistance', one as 'wheelchair-dependent', and two as 'severely immobile'. In addition to best supportive care, three patients had received haematopoietic stem cell transplantation (HSCT) and one had received velmanase alfa enzyme replacement therapy (ERT). Patient HRQoL results for the EQ-5D-5 L questionnaire and the Health Utilities Index-3 showed that patients with more severe ambulatory health states reported lower utility values than patients who were more mobile. Patients who received HSCT or ERT experienced improved HRQoL. Carer HRQoL results for the Hospital Anxiety and Depression Scale and Caregiver Strain Index demonstrated that carers experience high levels of stress and anxiety from their caregiving responsibilities.

Conclusions

This survey confirmed the heterogeneity of alpha-mannosidosis and the large impact of the disease and treatment on patients, carers, and families. Early diagnosis and access to treatment offers the best chance of slowing the disease progression and may provide some relief to patients and carers.

Hematopoietic Stem Cell Transplantation in Inborn Errors of Metabolism

Hematopoietic stem cell transplantation (HSCT) has been established as an effective therapy for selected inborn errors of metabolism. The success of HSCT in metabolic disease is best exemplified through the treatment of Hurler's syndrome, a lysosomal storage disease. Through the collaborative effort of several international centers, factors that predict successful patient and transplant outcomes have been identified. In this review, we discuss the principles that underlie the use of HSCT in metabolic diseases. We consider the clinical indications, conditioning regimens, and disease-specific follow-up for HSCT in different metabolic diseases. We highlight persisting challenges in HSCT to delay progression of certain organ systems that remain refractory to HSCT and the relatively high rates of aplastic graft failure. Finally, we evaluate the variable applicability of these principles to other inherited metabolic disorders including peroxisomal, mitochondrial, and other lysosomal storage diseases.

Alpha-Mannosidosis: Therapeutic Strategies

Alpha-mannosidosis (α-mannosidosis) is a rare lysosomal storage disorder with an autosomal recessive inheritance caused by mutations in the gene encoding for the lysosomal α-d-mannosidase. So far, 155 variants from 191 patients have been identified and in part characterized at the biochemical level. Similarly to other lysosomal storage diseases, there is no relationship between genotype and phenotype in alpha-mannosidosis. Enzyme replacement therapy is at the moment the most effective therapy for lysosomal storage disease, including alpha-mannosidosis. In this review, the genetic of alpha-mannosidosis has been described together with the results so far obtained by two different therapeutic strategies: bone marrow transplantation and enzyme replacement therapy. The primary indication to offer hematopoietic stem cell transplantation in patients affected by alpha-mannosidosis is preservation of neurocognitive function and prevention of early death. The results obtained from a Phase I⁻II study and a Phase III study provide evidence of the positive clinical effect of the recombinant enzyme on patients with alpha-mannosidosis.

amamutdb.no: A relational database for MAN2B1 allelic variants that compiles genotypes, clinical phenotypes, and biochemical and structural data of mutant MAN2B1 in α-mannosidosis

α-Mannosidosis is an autosomal recessive lysosomal storage disorder caused by mutations in the MAN2B1 gene, encoding lysosomal α-mannosidase. The disorder is characterized by a range of clinical phenotypes of which the major manifestations are mental impairment, hearing impairment, skeletal changes, and immunodeficiency. Here, we report an α-mannosidosis mutation database, amamutdb.no, which has been constructed as a publicly accessible online resource for recording and analyzing MAN2B1 variants (http://amamutdb.no). Our aim has been to offer structured and relational information on MAN2B1 mutations and genotypes along with associated clinical phenotypes. Classifying missense mutations, as pathogenic or benign, is a challenge. Therefore, they have been given special attention as we have compiled all available data that relate to their biochemical, functional, and structural properties. The α-mannosidosis mutation database is comprehensive and relational in the sense that information can be retrieved and compiled across datasets; hence, it will facilitate diagnostics and increase our understanding of the clinical and molecular aspects of α-mannosidosis. We believe that the amamutdb.no structure and architecture will be applicable for the development of databases for any monogenic disorder.

Delivering drugs to the central nervous system: an overview

Developing therapies for the brain is perhaps the greatest challenge facing modern medicine today. While a great many potential therapies show promise in animal models, precious few make it to approval or are even studied in human patients. The particular challenges to the translation of neurotherapeutics to the clinic are many, but a major barrier is difficulty in delivering therapeutics into the brain. The goal of this workshop was to present ways to deliver therapeutics to the brain, including the limitations of each method, and describe ways to track their delivery, safety, and efficacy. Solving the problem of delivery will aid translation of therapeutics for patients suffering from neurodegeneration and other disorders of the brain.

Successful unrelated bone marrow transplantation in two siblings with alpha-mannosidosis

Alpha-mannosidosis is a rare lysosomal storage disorder with an autosomal recessive inheritance. Deficient alpha-mannosidase activity leads to lysosomal accumulation of mannose-rich oligosaccharides. The disease characterized by mental retardation, skeletal changes, hearing impairment, and recurrent infections. Stem cell transplantation has been shown to be an effective treatment. It works by providing increased levels of α-mannosidase in the localized extracellular milieu to provide improvements in skeletal malformations, neurocognitive, and sensorineural function. In this case report, we describe a pair of siblings with α-mannosidosis who successfully underwent HSCT from matched unrelated donors. In both siblings, enzyme levels reached to normal limits and improvements in clinical symptoms were recognized early after HSCT. We conclude that HSCT should be considered as a therapeutic approach in patients with alpha-mannosidosis before disease-related complications have developed.