Hepatomegaly and Splenomegaly: An Approach to the Diagnosis of Lysosomal Storage Diseases.

Clinical findings of hepatomegaly and splenomegaly, the abnormal enlargement of the liver and spleen, respectively, should prompt a broad differential diagnosis that includes metabolic, congestive, neoplastic, infectious, toxic, and inflammatory conditions. Among the metabolic diseases, lysosomal storage diseases (LSDs) are a group of rare and ultrarare conditions with a collective incidence of 1 in 5000 live births. LSDs are caused by genetic variants affecting the lysosomal enzymes, transporters, or integral membrane proteins. As a result, abnormal metabolites accumulate in the organelle, leading to dysfunction. Therapeutic advances, including early diagnosis and disease-targeted management, have improved the life expectancy and quality of life of people affected by certain LSDs. To access these new interventions, LSDs must be considered in patients presenting with hepatomegaly and splenomegaly throughout the lifespan. This review article navigates the diagnostic approach for individuals with hepatosplenomegaly particularly focusing on LSDs. We provide hints in the history, physical exam, laboratories, and imaging that may identify LSDs. Additionally, we discuss molecular testing, arguably the preferred confirmatory test (over biopsy), accompanied by enzymatic testing when feasible.

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.

Higher precision, first tier newborn screening for metachromatic leukodystrophy using 16:1-OH-sulfatide.

Newborn screening (NBS) for metachromatic leukodystrophy (MLD) is based on first-tier measurement of sulfatides in dried blood spots (DBS) followed by second-tier measurement of arylsulfatase A in the same DBS. This approach is very precise with 0-1 false positives per ∼30,000 newborns tested. Recent data reported here shows that the sulfatide molecular species with an α-hydroxyl, 16­carbon, mono-unsaturated fatty acyl group (16:1-OH-sulfatide) is superior to the original biomarker 16:0-sulfatide in reducing the number of first-tier false positives. This result is consistent across 4 MLD NBS centers. By measuring 16:1-OH-sulfatide alone or together with 16:0-sulfatide, the estimated false positive rate is 0.048% and is reduced essentially to zero with second-tier arylsulfatase A activity assay. The false negative rate is predicted to be extremely low based on the demonstration that 40 out of 40 newborn DBS from clinically-confirmed MLD patients are detected with these methods. The work shows that NBS for MLD is extremely precise and ready for deployment. Furthermore, it can be multiplexed with several other inborn errors of metabolism already tested in NBS centers worldwide.

Long-term outcomes in two adult siblings with Fucosidosis - Diagnostic odyssey and clinical manifestations.

Fucosidosis (OMIN# 230000) is a rare lysosomal storage disorder (LSDs) caused by mutations in the FUCA1 gene, leading to alpha-L-fucosidase deficiency; it is inherited as an autosomal recessive trait. Fucosidosis represents a disease spectrum with a wide variety of clinical features, but most affected patients have slow neurologic deterioration. Many patients die young and the long-term clinical outcomes in adult patients are poorly documented. Here, we report the long-term follow up of two Caucasian siblings, a 31-year-old man and 25-year-old woman. We describe the clinical, biochemical, radiological and genetic findings in two siblings affected by Fucosidosis and the differences between them after 19-years follow up. The dermatological features of the younger sibling have been reported previously by Bharati et al. (2007). Both patients have typical features of Fucosidosis, such as learning difficulties, ataxia, and angiokeratomas with differing severity. Case 1 presents severe ataxia with greater limitation of mobility, multiple dysostoses, angiokeratomas on his limbs, retinal vein enlargement and increased tortuosity in the eye and gastrointestinal symptoms. Biochemical analysis demonstrated a deficiency of alpha-fucosidase in leucocytes. Case 2 has a greater number of angiokeratomas and has suffered three psychotic episodes. The diagnosis of Fucosidosis was confirmed in cultured skin fibroblast at the age of 12 years. Molecular analysis of the FUCA1 gene showed a heterozygous mutation c.998G > A p.(Gly333Asp), with a pathogenic exon 4 deletion in the other allele in both patients. Conclusion. Fucosidosis presents a wide clinical heterogeneity and intrafamilial variability of symptoms. Psychosis and gastrointestinal symptoms have not been reported previously in Fucosidosis.

Defect-free graphene enhances enzyme delivery to fibroblasts derived from patients with lysosomal storage disorders.

Enzyme replacement therapy shows remarkable clinical improvement in treating lysosomal storage disorders. However, this therapeutic approach is hampered by limitations in the delivery of the enzyme to cells and tissues. Therefore, there is an urgent, unmet clinical need to develop new strategies to enhance the enzyme delivery to diseased cells. Graphene-based materials, due to their dimensionality and favourable pattern of interaction with cells, represent a promising platform for the loading and delivery of therapeutic cargo. Herein, the potential use of graphene-based materials, including defect-free graphene with positive or negative surface charge and graphene oxide with different lateral dimensions, was investigated for the delivery of lysosomal enzymes in fibroblasts derived from patients with Mucopolysaccharidosis VI and Pompe disease. We report excellent biocompatibility of all graphene-based materials up to a concentration of 100 µg mL-1 in the cell lines studied. In addition, a noticeable difference in the uptake profile of the materials was observed. Neither type of graphene oxide was taken up by the cells to a significant extent. In contrast, the two types of graphene were efficiently taken up, localizing in the lysosomes. Furthermore, we demonstrate that cationic graphene flakes can be used as carriers for arylsulfatase B enzyme, for the delivery of the lacking enzyme to the lysosomes of Mucopolysaccharidosis VI fibroblasts. Arylsulfatase B complexed with cationic graphene flakes not only retained the enzymatic activity, but also exerted biological effects almost twice as high as arylsulfatase B alone in the clearance of the substrate in Mucopolysaccharidosis VI fibroblasts. This study lays the groundwork for the potential use of graphene-based materials as carriers for enzyme replacement therapy in lysosomal storage disorders.

Reply to Maase et al. Comment on "Jones et al. Application of a Novel Algorithm for Expanding Newborn Screening for Inherited Metabolic Disorders across Europe. Int. J. Neonatal Screen. 2022, 8, 20".

The commentary provided by Maase et al. [...].

Secondary Mitochondrial Dysfunction as a Cause of Neurodegenerative Dysfunction in Lysosomal Storage Diseases and an Overview of Potential Therapies.

Mitochondrial dysfunction has been recognised a major contributory factor to the pathophysiology of a number of lysosomal storage disorders (LSDs). The cause of mitochondrial dysfunction in LSDs is as yet uncertain, but appears to be triggered by a number of different factors, although oxidative stress and impaired mitophagy appear to be common inhibitory mechanisms shared amongst this group of disorders, including Gaucher's disease, Niemann-Pick disease, type C, and mucopolysaccharidosis. Many LSDs resulting from defects in lysosomal hydrolase activity show neurodegeneration, which remains challenging to treat. Currently available curative therapies are not sufficient to meet patients' needs. In view of the documented evidence of mitochondrial dysfunction in the neurodegeneration of LSDs, along with the reciprocal interaction between the mitochondrion and the lysosome, novel therapeutic strategies that target the impairment in both of these organelles could be considered in the clinical management of the long-term neurodegenerative complications of these diseases. The purpose of this review is to outline the putative mechanisms that may be responsible for the reported mitochondrial dysfunction in LSDs and to discuss the new potential therapeutic developments.

Juvenile mucopolysaccharidosis plus disease caused by a missense mutation in VPS33A.

A rare and fatal disease resembling mucopolysaccharidosis in infants, is caused by impaired intracellular endocytic trafficking due to deficiency of core components of the intracellular membrane-tethering protein complexes, HOPS, and CORVET. Whole exome sequencing identified a novel VPS33A mutation in a patient suffering from a variant form of mucopolysaccharidosis. Electron and confocal microscopy, immunoblotting, and glycosphingolipid trafficking experiments were undertaken to investigate the effects of the mutant VPS33A in patient-derived skin fibroblasts. We describe an attenuated juvenile form of VPS33A-related syndrome-mucopolysaccharidosis plus in a man who is homozygous for a hitherto unknown missense mutation (NM_022916.4: c.599 G>C; NP_075067.2:p. Arg200Pro) in a conserved region of the VPS33A gene. Urinary glycosaminoglycan (GAG) analysis revealed increased heparan, dermatan sulphates, and hyaluronic acid. We showed decreased abundance of VPS33A in patient derived fibroblasts and provided evidence that the p.Arg200Pro mutation leads to destablization of the protein and proteasomal degradation. As in the infantile form of mucopolysaccharidosis plus, the endocytic compartment in the fibroblasts also expanded-a phenomenon accompanied by increased endolysosomal acidification and impaired intracellular glycosphingolipid trafficking. Experimental treatment of the patient's cultured fibroblasts with the proteasome inhibitor, bortezomib, or exposure to an inhibitor of glucosylceramide synthesis, eliglustat, improved glycosphingolipid trafficking. To our knowledge this is the first report of an attenuated juvenile form of VPS33A insufficiency characterized by appreciable residual endosomal-lysosomal trafficking and a milder mucopolysaccharidosis plus than the disease in infants. Our findings expand the proof of concept of redeploying clinically approved drugs for therapeutic exploitation in patients with juvenile as well as infantile forms of mucopolysaccharidosis plus disease.

A New Approach to Objectively Evaluate Inherited Metabolic Diseases for Inclusion on Newborn Screening Programmes.

Newborn screening (NBS) programmes are essential in the diagnosis of inherited metabolic diseases (IMDs) and for access to disease modifying treatment. Most European countries follow the World Health Organisation (WHO) criteria to determine which disorders are appropriate for screening at birth; however, these criteria are interpreted and implemented by individual countries differently, creating disparities. Advances in research and diagnostics, together with the promise of new treatments, offer new possibilities to accelerate the expansion of evidence-based screening programmes. A novel and robust algorithm was built to objectively assess and prioritise IMDs for inclusion in NBS programmes. The Wilson and Jungner classic screening principles were used as a foundation to develop individual and measurable criteria. The proposed algorithm is a point-based system structured upon three pillars: condition, screening, and treatment. The algorithm was tested by applying the six IMDs currently approved in the United Kingdom NBS programme. The algorithm generates a weight-based score that could be used as the first step in the complex process of evaluating disorders for inclusion on NBS programmes. By prioritising disorders to be further evaluated, individual countries are able to assess the economic, societal and political aspects of a potential screening programme.

Application of a Novel Algorithm for Expanding Newborn Screening for Inherited Metabolic Disorders across Europe.

Inherited metabolic disorders (IMDs) are mostly rare, have overlapping symptoms, and can be devastating and progressive. However, in many disorders, early intervention can improve long-term outcomes, and newborn screening (NBS) programmes can reduce caregiver stress in the journey to diagnosis and allow patients to receive early, and potentially pre-symptomatic, treatment. Across Europe there are vast discrepancies in the number of IMDs that are screened for and there is an imminent opportunity to accelerate the expansion of evidence-based screening programmes and reduce the disparities in screening programmes across Europe. A comprehensive list of IMDs was created for analysis. A novel NBS evaluation algorithm, described by Burlina et al. in 2021, was used to assess and prioritise IMDs for inclusion on expanded NBS programmes across Europe. Forty-eight IMDs, of which twenty-one were lysosomal storage disorders (LSDs), were identified and assessed with the novel NBS evaluation algorithm. Thirty-five disorders most strongly fulfil the Wilson and Jungner classic screening principles and should be considered for inclusion in NBS programmes across Europe. The recommended disorders should be evaluated at the national level to assess the economic, societal, and political aspects of potential screening programmes.

Advance Care Planning for Individuals With Intellectual and Developmental Disabilities: A State-by-State Content Analysis of Person-Centered Service Plans.

Older adults are a rapidly growing segment of the intellectual and developmental disabilities (IDD) population. Advance care planning (ACP) is recommended as a best practice for adults with IDD, yet, adoption remains low. For individuals receiving Medicaid services, regular meetings maintain the person-centered planning (PCP) process. Content analysis was used to examine data from public documents across the United States to identify the frequency of ACP in PCP and the ways it manifests. Results indicate most states had evidence of ACP within the PCP process with notable variation to the extent. Findings suggest many PCP documents lack content specific to late-life transitions. Included are examples of the ways states have integrated ACP into PCP that can serve as a guide.

Enzyme replacement therapy and hematopoietic stem cell transplant: a new paradigm of treatment in Wolman disease.

BACKGROUND: Wolman disease is a rare, lysosomal storage disorder in which biallelic variants in the LIPA gene result in reduced or complete lack of lysosomal acid lipase. The accumulation of the substrates; cholesterol esters and triglycerides, significantly impacts cellular function. Untreated patients die within the first 12 months of life. Clinically, patients present severely malnourished, with diarrhoea and hepatosplenomegaly, many have an inflammatory phenotype, including with hemophagocytic lymphohistiocytosis (HLH). Hematopoietic stem cell transplant (HCT) had been historically the only treatment available but has a high procedure-related mortality because of disease progression and disease-associated morbidities. More recently, enzyme replacement therapy (ERT) with dietary substrate reduction (DSR) has significantly improved patient survival. However, ERT is life long, expensive and its utility is limited by anti-drug antibodies (ADA) and the need for central venous access. RESULTS: We describe five Wolman disease patients diagnosed in infancy that were treated at Royal Manchester Children's Hospital receiving ERT with DSR then HCT-multimodal therapy. In 3/5 an initial response to ERT was attenuated by ADA with associated clinical and laboratory features of deterioration. 1/5 developed anaphylaxis to ERT and the other patient died post HCT with ongoing HLH. All patients received allogeneic HCT. 4/5 patients are alive, and both disease phenotype and laboratory parameters are improved compared to when they were on ERT alone. The gastrointestinal symptoms are particularly improved after HCT, with reduced diarrhoea and vomiting. This allows gradual structured normalisation of diet with improved tolerance of dietary fat. Histologically there are reduced cholesterol clefts, fewer foamy macrophages and an improved villous structure. Disease biomarkers also show improvement with ERT, immunotherapy and HCT. Three patients have mixed chimerism after HCT, indicating a likely engraftment-defect in this condition. CONCLUSION: We describe combined ERT, DSR and HCT, multimodal treatment for Wolman disease. ERT and DSR stabilises the sick infant and reduces the formerly described prohibitively high, transplant-associated mortality in this condition. HCT abrogates the problems of ERT, namely attenuating ADA, the need for continuing venous access, and continuing high cost drug treatment. HCT also brings improved efficacy, particularly evident in improved gastrointestinal function and histology. Multimodal therapy should be considered a new paradigm of treatment for Wolman disease patients where there is an attenuated response to ERT, and for all patients where there is a well-matched transplant donor, in order to improve long term gut function, tolerance of a normal diet and quality of life.

A deletion of IDUA exon 10 in a family of Golden Retriever dogs with an attenuated form of mucopolysaccharidosis type I.

BACKGROUND: Mucopolysaccharidosis type I (MPS-I) is a lysosomal storage disorder caused by a deficiency of the enzyme α-l-iduronidase, leading to accumulation of undegraded dermatan and heparan sulfates in the cells and secondary multiorgan dysfunction. In humans, depending upon the nature of the underlying mutation(s) in the IDUA gene, the condition presents with a spectrum of clinical severity. OBJECTIVES: To characterize the clinical and biochemical phenotypes, and the genotype of a family of Golden Retriever dogs. ANIMALS: Two affected siblings and 11 related dogs. METHODS: Family study. Urine metabolic screening and leucocyte lysosomal enzyme activity assays were performed for biochemical characterization. Whole genome sequencing was used to identify the causal mutation. RESULTS: The clinical signs shown by the proband resemble the human attenuated form of the disease, with a dysmorphic appearance, musculoskeletal, ocular and cardiac defects, and survival to adulthood. Urinary metabolic studies identified high levels of dermatan sulfate, heparan sulfate, and heparin. Lysosomal enzyme activities demonstrated deficiency in α-l-iduronidase activity in leucocytes. Genome sequencing revealed a novel homozygous deletion of 287 bp resulting in full deletion of exon 10 of the IDUA gene (NC_006585.3(NM_001313883.1):c.1400-76_1521+89del). Treatment with pentosan polyphosphate improved the clinical signs until euthanasia at 4.5 years. CONCLUSION AND CLINICAL IMPORTANCE: Analysis of the genotype/phenotype correlation in this dog family suggests that dogs with MPS-I could have a less severe phenotype than humans, even in the presence of severe mutations. Treatment with pentosan polyphosphate should be considered in dogs with MPS-I.

The lysosomal disease caused by mutant VPS33A.

A rare lysosomal disease resembling a mucopolysaccharidosis with unusual systemic features, including renal disease and platelet dysfunction, caused by the defect in a conserved region of the VPS33A gene on human chromosome 12q24.31, occurs in Yakuts-a nomadic Turkic ethnic group of Southern Siberia. VPS33A is a core component of the class C core vacuole/endosome tethering (CORVET) and the homotypic fusion and protein sorting (HOPS) complexes, which have essential functions in the endocytic pathway. Here we show that cultured fibroblasts from patients with this disorder have morphological changes: vacuolation with disordered endosomal/lysosomal compartments and-common to sphingolipid diseases-abnormal endocytic trafficking of lactosylceramide. Urine glycosaminoglycan studies revealed a pathological excess of sialylated conjugates as well as dermatan and heparan sulphate. Lipidomic screening showed elevated ß-D-galactosylsphingosine with unimpaired activity of cognate lysosomal hydrolases. The 3D crystal structure of human VPS33A predicts that replacement of arginine 498 by tryptophan will de-stabilize VPS33A folding. We observed that the missense mutation reduced the abundance of full-length VPS33A and other components of the HOPS and CORVET complexes. Treatment of HeLa cells stably expressing the mutant VPS33A with a proteasome inhibitor rescued the mutant protein from degradation. We propose that the disease is due to diminished intracellular abundance of intact VPS33A. Exposure of patient-derived fibroblasts to the clinically approved proteasome inhibitor, bortezomib, or inhibition of glucosylceramide synthesis with eliglustat, partially corrected the impaired lactosylceramide trafficking defect and immediately suggest therapeutic avenues to explore in this fatal orphan disease.

Impact of Caregiver Burden on Quality of Life for Parents of Adult Children With Autism Spectrum Disorder.

This study sought to examine the impact of time, developmental, emotional, and financial burdens on the quality of life (QOL) for parents (aged 50+) of an adult child with autism spectrum disorder (ASD). Participants ( N = 320) completed a web-based survey and could indicate interest in participating in one-on-one follow up interviews. Multiple linear regression analysis indicated that two variables, developmental burden and impact of caregiving on finances, were statistically significant predictors of parents' QOL. Developmental burden was the strongest predictor of parental QOL, demonstrating an inverse relationship. Qualitatively, reported findings indicated that many parents were experiencing all four burdens. Findings highlighted the need to provide services and supports to alleviate burden among aging parents of adult children with ASD.

A decade of excellent transplant survival in children with inherited metabolic diseases: A report from a single metabolic transplant centre in Europe.

Hematopoietic cell transplantation (HCT) confers a long-term disease-modifying therapy for transplant-permissive inherited metabolic diseases (IMDs). We examined the overall survival (OS) and engrafted survival (ES) of children with IMDs, who received first HCT at Royal Manchester Children's hospital from 1985 to 2016. A total of 137 children with IMDs were included in this analysis (historical cohort [1985-2006], n＝65; current cohort [2007-2016], n＝72). Primary diagnoses included mucopolysaccharidoses (81%), X-linked adrenoleukodystrophy (6%), metachromatic leukodystrophy (4%), mannosidosis (3%), Wolman disease (2%), and other conditions (4%). The five-year OS has increased from 65% (95% confidence interval [CI], 52%-76%) in the historical cohort to 91% (95% CI, 81%-96%) in the current cohort (P<0.001). Moreover, the five-year ES, which was 64% (95 CI%, 56%-72%) for the entire cohort, has doubled from 41% (95% CI, 29%-53%) in the historical cohort to 85% (95% CI, 75%-92%) in the current cohort (P<0.001). The proportion of patients with graft failure has decreased from 37% in the historical cohort to 8% in the current cohort (P<0.001). In patients who received a second transplant, 13 out of 20 patients (65%) in the historical cohort and all four in the current cohort were alive and engrafted. Of 82 survivors followed-up at Manchester, 80% and 20% had full and mixed chimerism, respectively. Although this study was restricted to a single center, our findings show that HCT is an increasingly safe procedure and provides long-lasting endogenous enzyme replacement therapy for children with IMDs in the modern era of HCT.

The effect of haemopoietic stem cell transplantation on the ocular phenotype in mucopolysaccharidosis type I (Hurler).

PURPOSE: To determine whether the ocular phenotype in patients with mucopolysaccharidosis type I (MPSI) Hurler is affected by the efficacy of previous haemopoietic stem cell transplantation (HSCT). DESIGN: A retrospective cohort study of patients with MPSI who had undergone treatment with HSCT. METHODS: Ocular phenotype was documented for each patient and compared to levels of biomarkers representing efficacy of previous transplantation. MAIN OUTCOME MEASURES: Assessment of visual acuity (VA), severity of corneal clouding and the presence of optic neuropathy or retinopathy. Biomarker assessment included dermatan sulphate/chondroitin sulphate (DS/CS) ratio and iduronidase enzyme level. RESULTS: Severe corneal clouding was significantly greater in patients with lower iduronidase levels (p = 0.023) and raised DS/CS ratio (R2  = 0.28 p = 0.043). Better VA was related to a higher iduronidase levels (R2  = 0.15, p = 0.004) and lower DS/CS ratio (R2  = 0.38, p = 0.001). CONCLUSION: Improved ocular phenotypes in MPSI are associated with markers signifying efficacy of prior transplant. Early and effective HSCT may result in a better visual prognosis and reduction in ocular complications for patients with MPSI.

Haematopoietic Stem Cell Transplantation Arrests the Progression of Neurodegenerative Disease in Late-Onset Tay-Sachs Disease.

Tay-Sachs disease is a rare metabolic disease caused by a deficiency of hexosaminidase A that leads to accumulation of GM2 gangliosides predominantly in neural tissue. Late-onset Tay-Sachs disease variant is associated with a higher level of residual HexA activity. Treatment options are limited, and there are a few described cases who have undergone haematopoietic stem cell transplantation (HSCT) with variable outcome.We describe a case of a 23-year-old male patient who presented with a long-standing tremor since 7 years of age. He had gait ataxia, a speech stammer and swallowing problems. His condition had had a static course apart from his tremor that had been gradually deteriorating. Because of the deterioration in his neurological function, the patient had an uneventful, matched-sibling donor bone marrow transplant at the age of 15 years. Eight years post-HSCT, at the age of 23, he retains full donor engraftment, and his white cell beta-HexA of 191 nmol/mg/h is comparable to normal controls (in-assay control = 187). He continues to experience some intentional tremor that is tolerable for daily life and nonprogressive since HSCT. CONCLUSION: HSCT is a potential treatment option which might arrest neurodegeneration in patients with LOTS.

IDUA mutational profile and genotype-phenotype relationships in UK patients with Mucopolysaccharidosis Type I.

Mucopolysaccharidosis Type I (MPS I) is a lysosomal storage disorder with varying degrees of phenotypic severity caused by mutations in IDUA. Over 200 disease-causing variants in IDUA have been reported. We describe the profile of disease-causing variants in 291 individuals with MPS I for whom IDUA sequencing was performed, focusing on the UK subset of the cohort. A total of 63 variants were identified, of which 20 were novel, and the functional significance of the novel variants is explored. The severe form of MPS I is treated with hematopoietic stem cell transplantation, known to have improved outcomes with earlier age at treatment. Developing genotype-phenotype relationships would therefore have considerable clinical utility, especially in the light of the development of newborn screening programs for MPS I. Associations between genotype and phenotype are examined in this cohort, particularly in the context of the profile of variants identified in UK individuals. Relevant associations can be made for the majority of UK individuals based on the presence of nonsense or truncating variants as well as other associations described in this report.

Long term survival and cardiopulmonary outcome in children with Hurler syndrome after haematopoietic stem cell transplantation.

Premature death in untreated children with Hurler syndrome (HS) in the first decade of life is largely due to life-threatening cardiopulmonary complications. We examined the long-term survival and cardiopulmonary outcome in 54 children undergoing haematopoietic stem cell transplantation (HSCT) at the Royal Manchester Children's Hospital from 1985 to 2008. The median age at first HSCT was 15.1 months. Eighteen had graft failure and nine died after first HSCT. Of 18 patients with graft failure, 17 underwent second HSCT and the remaining one was lost to follow-up (LOF). Twelve were alive-and-engrafted after second HSCT. The overall survival at one year and 20-years was the same at 73.7%. Six children were followed up at the referral centers and excluded from cardiopulmonary endpoint review. Of the 33 evaluable children for the cardiopulmonary endpoints, nine (27.3%) had normal cardiac assessment. Of the four children on angiotensin-converting-enzyme inhibitors, two had mild cardiomyopathy and two had aortic valvular replacement. Twenty (60%) had mild/moderate mitral and/or aortic insufficiencies. Two had overnight hypoxia needing nocturnal non-invasive support. Enzyme level and donor chimerism are important predictors of long-term cardiac outcome.