Neurocognitive outcome and mental health in children with tyrosinemia type 1 and phenylketonuria: A comparison between two genetic disorders affecting the same metabolic pathway.

Tyrosinemia type 1 (TT1) and phenylketonuria (PKU) are both inborn errors of phenylalanine-tyrosine metabolism. Neurocognitive and behavioral outcomes have always featured in PKU research but received less attention in TT1 research. This study aimed to investigate and compare neurocognitive, behavioral, and social outcomes of treated TT1 and PKU patients. We included 33 TT1 patients (mean age 11.24 years; 16 male), 31 PKU patients (mean age 10.84; 14 male), and 58 age- and gender-matched healthy controls (mean age 10.82 years; 29 male). IQ (Wechsler-subtests), executive functioning (the Behavioral Rating Inventory of Executive Functioning), mental health (the Achenbach-scales), and social functioning (the Social Skills Rating System) were assessed. Results of TT1 patients, PKU patients, and healthy controls were compared using Kruskal-Wallis tests with post-hoc Mann-Whitney U tests. TT1 patients showed a lower IQ and poorer executive functioning, mental health, and social functioning compared to healthy controls and PKU patients. PKU patients did not differ from healthy controls regarding these outcome measures. Relatively poor outcomes for TT1 patients were particularly evident for verbal IQ, BRIEF dimensions "working memory", "plan and organize" and "monitor", ASEBA dimensions "social problems" and "attention problems", and for the SSRS "assertiveness" scale (all p values <0.001). To conclude, TT1 patients showed cognitive impairments on all domains studied, and appeared to be significantly more affected than PKU patients. More attention should be paid to investigating and monitoring neurocognitive outcome in TT1 and research should focus on explaining the underlying pathophysiological mechanism.

Oral pharmacological chaperone migalastat compared with enzyme replacement therapy in Fabry disease: 18-month results from the randomised phase III ATTRACT study.

BACKGROUND: Fabry disease is an X-linked lysosomal storage disorder caused by GLA mutations, resulting in α-galactosidase (α-Gal) deficiency and accumulation of lysosomal substrates. Migalastat, an oral pharmacological chaperone being developed as an alternative to intravenous enzyme replacement therapy (ERT), stabilises specific mutant (amenable) forms of α-Gal to facilitate normal lysosomal trafficking. METHODS: The main objective of the 18-month, randomised, active-controlled ATTRACT study was to assess the effects of migalastat on renal function in patients with Fabry disease previously treated with ERT. Effects on heart, disease substrate, patient-reported outcomes (PROs) and safety were also assessed. RESULTS: Fifty-seven adults (56% female) receiving ERT (88% had multiorgan disease) were randomised (1.5:1), based on a preliminary cell-based assay of responsiveness to migalastat, to receive 18 months open-label migalastat or remain on ERT. Four patients had non-amenable mutant forms of α-Gal based on the validated cell-based assay conducted after treatment initiation and were excluded from primary efficacy analyses only. Migalastat and ERT had similar effects on renal function. Left ventricular mass index decreased significantly with migalastat treatment (-6.6 g/m2 (-11.0 to -2.2)); there was no significant change with ERT. Predefined renal, cardiac or cerebrovascular events occurred in 29% and 44% of patients in the migalastat and ERT groups, respectively. Plasma globotriaosylsphingosine remained low and stable following the switch from ERT to migalastat. PROs were comparable between groups. Migalastat was generally safe and well tolerated. CONCLUSIONS: Migalastat offers promise as a first-in-class oral monotherapy alternative treatment to intravenous ERT for patients with Fabry disease and amenable mutations. TRIAL REGISTRATION NUMBER: NCT00925301; Pre-results.

International clinical guideline for the management of classical galactosemia: diagnosis, treatment, and follow-up.

Classical galactosemia (CG) is an inborn error of galactose metabolism. Evidence-based guidelines for the treatment and follow-up of CG are currently lacking, and treatment and follow-up have been demonstrated to vary worldwide. To provide patients around the world the same state-of-the-art in care, members of The Galactosemia Network (GalNet) developed an evidence-based and internationally applicable guideline for the diagnosis, treatment, and follow-up of CG. The guideline was developed using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) system. A systematic review of the literature was performed, after key questions were formulated during an initial GalNet meeting. The first author and one of the working group experts conducted data-extraction. All experts were involved in data-extraction. Quality of the body of evidence was evaluated and recommendations were formulated. Whenever possible recommendations were evidence-based, if not they were based on expert opinion. Consensus was reached by multiple conference calls, consensus rounds via e-mail and a final consensus meeting. Recommendations addressing diagnosis, dietary treatment, biochemical monitoring, and follow-up of clinical complications were formulated. For all recommendations but one, full consensus was reached. A 93 % consensus was reached on the recommendation addressing age at start of bone density screening. During the development of this guideline, gaps of knowledge were identified in most fields of interest, foremost in the fields of treatment and follow-up.

Mutation of the iron-sulfur cluster assembly gene IBA57 causes severe myopathy and encephalopathy.

Two siblings from consanguineous parents died perinatally with a condition characterized by generalized hypotonia, respiratory insufficiency, arthrogryposis, microcephaly, congenital brain malformations and hyperglycinemia. Catalytic activities of the mitochondrial respiratory complexes I and II were deficient in skeletal muscle, a finding suggestive of an inborn error in mitochondrial biogenesis. Homozygosity mapping identified IBA57 located in the largest homozygous region on chromosome 1 as a culprit candidate gene. IBA57 is known to be involved in the biosynthesis of mitochondrial [4Fe-4S] proteins. Sequence analysis of IBA57 revealed the homozygous mutation c.941A > C, p.Gln314Pro. Severely decreased amounts of IBA57 protein were observed in skeletal muscle and cultured skin fibroblasts from the affected subjects. HeLa cells depleted of IBA57 showed biochemical defects resembling the ones found in patient-derived cells, including a decrease in various mitochondrial [4Fe-4S] proteins and in proteins covalently linked to lipoic acid (LA), a cofactor produced by the [4Fe-4S] protein LA synthase. The defects could be complemented by wild-type IBA57 and partially by mutant IBA57. As a result of the mutation, IBA57 protein was excessively degraded, an effect ameliorated by protease inhibitors. Hence, we propose that the mutation leads to partial functional impairment of IBA57, yet the major pathogenic impact is due to its proteolytic degradation below physiologically critical levels. In conclusion, the ensuing lethal complex biochemical phenotype of a novel metabolic syndrome results from multiple Fe/S protein defects caused by a deficiency in the Fe/S cluster assembly protein IBA57.

Left ventricular hypertrophy: do not forget Fabry disease. Diagnostic work-up and differential diagnosis.

BACKGROUND: Left ventricular (LV) hypertrophy is a common clinical finding. Differential diagnosis includes Fabry disease, a rare and progressive, but treatable storage disease caused by deficiency of α-galactosidase A. However, diagnosis of Fabry is often hampered by its clinical heterogeneity, LV hypertrophy phenocopies and unawareness of the clinician. METHODS: This review summarises clinical data, family history, electrocardiogram (ECG) and imaging (echocardiogram and cardiovascular magnetic resonance (CMR)) characteristics to differentiate aetiologies of LV hypertrophy including clues for the diagnosis of Fabry. RESULTS: LV hypertrophy is a consequence of pressure overload mostly, but differential diagnosis includes hypertrophic cardiomyopathy and infiltrative diseases. Clinical data, ECG, type and degree of LV hypertrophy, functional and tissue characteristics differ among aetiologies. LV hypertrophy in Fabry is progressive and mostly concentric but may copy any hypertrophic cardiomyopathy. Dependent on residual alfa-galactosidase A enzyme activity, degree of LV hypertrophy in Fabry may vary. Initially, low myocardial CMR T1-map values are calculated. At a later stage, midwall late gadolinium enhancement of the inferolateral LV wall may occur. Global longitudinal strain may be depressed in the inferolateral wall. Voltage criteria for LV hypertrophy and short PQ interval are common. Right ventricular (RV) hypertrophy is frequent. In addition, multisystemic symptoms including neuropathic pain, hypohidrosis, proteinuria, renal insufficiency and familial young stroke are pointing to Fabry. CONCLUSIONS: LV hypertrophy should raise suspicion of Fabry disease, especially if LV hypertrophy is unexplained and/or associated with RV hypertrophy. In Fabry, LV hypertrophy may be heterogeneous and mimic any hypertrophic cardiomyopathy. ECG, multisystemic symptoms and imaging may provide clues for Fabry.

Severe dilated cardiomyopathy as an unusual clinical presentation in an infant with sialidosis type II.

We report a unique case of an infant with a severe dilated cardiomyopathy as the clinical presentation of sialidosis type II (OMIM 256550), a rare autosomal recessive inherited lysosomal storage disease that is characterized by partial or complete deficiency of α-neuraminidase, following mutations in the gene neuraminidase 1 (NEU1), located on the short arm of chromosome 6 (6p21.3). Accumulation of metabolic intermediates leads to severe morbidity, especially myoclonus, gait disturbances, cherry-red macules with secondary loss of visual acuity, impaired color vision and night blindness, and sometimes additional neurological findings such as seizures. Dilated cardiomyopathies are characterized by dilation and impaired contraction of the left or both ventricles, whereas most of the metabolic cardiomyopathies are hypertrophic forms appearing with diastolic dysfunction and, in case of lysosomal storage diseases, often associated with valvular thickening and prolapse. Cardiac manifestations in systemic storage disorders are common although rarely described in mucolipidoses. In mucolipidosis type 2 or I-cell disease only three cases were presented with severe dilated cardiomyopathy and endocardial fibroelastosis in infancy, as opposed to sialidosis type II, by which to the best of our knowledge no presentation of dilated cardiomyopathy was previously reported in literature.

A new multiplex analysis of glucosylsphingosine and globotriaosylsphingosine in dried blood spots by tandem mass spectrometry.

Background: Gaucher's and Fabry's disease are two of the most common treatable lysosomal storage diseases, and have a wide spectrum of clinical symptoms. Early detection is important, because timely initiation of treatments can improve the disease status and prevent complications. However disease manifestations develop in childhood, diagnosis is delayed until adulthood partly due to the limitations of the currently used diagnostic pathway. The aim of this research is to develop and validate a multiplex assay and defining reference ranges, which do not exist at this moment, to improve and facilitate the entire diagnostic work up and enable treatment in an earlier stage of disease. Methods and findings: Biomarkers glucosylsphingosine (GlcSph) and globotriaosylsphingosine (Lyso-Gb3) were detected and quantified using LC-MS/MS on dried blood spots. We developed an improved and new extraction method that allowed to measure GlcSph and Lyso-Gb3 in a multiplex analytical platform. After validation of the method, samples of 1480 individuals with normal enzymatic activity were collected to determine age and gender-related reference ranges.Our combination method showed a good linearity, precision, accuracy and limit of quantification with lack of carry-over following the specific international CLSI guidelines. The suggested protocol is robust, efficient, sensitive, specific, comprehensive and relatively cheap in order to accelerate the diagnostic process for both lysosomal storage diseases. The samples, with normal enzymatic activity, defined statistical relevant and clinical correct reference ranges for each specific age group by gender. Conclusion: We report a multiplex LC-MS/MS method and relevant reference ranges that are appropriate for the targeted screening, diagnosis and follow-up of Fabry and Gaucher disease.

What Mothers Know about Newborn Bloodspot Screening and the Sources They Use to Acquire This Knowledge: A Pilot Study in Flanders.

To learn what mothers know about newborn bloodspot screening (NBS), the procedure, and the sources used, a pilot study was performed. An online questionnaire was developed, with the first part focused on characteristics and the NBS procedure, and the second on knowledge, information sources, and health care providers (HCPs). This questionnaire was accessible until 200 answers were received. The characteristics of respondents were representative for the population. Mothers gave verbal consent in 69.5% of cases, 12.5% did not, and 18% stated that no consent was requested. The 'knowledge' part contained 12 closed questions, five multiple-choice questions on sources, and assessments (5-point Likert scores) of the information transfer. The mean knowledge level was 7.2/12. Screening concepts (consequences, likelihood, sensitivity, carrier) and absence of notification of normal findings were well known. The fact that NBS is not compulsory was poorly known, and post-analysis sample handling procedures were poorly understood. Key HCPs were midwifes (80.5%) and nurses (38.5%). When the leaflet (44%) was provided, the majority read it. Mean Likert scores were 3.36, 3.38, 3.11 and 3.35 for clarity, timing appropriateness, sufficiency, and usefulness. The knowledge level and consent practices were reasonably good. Key HCP were midwives and nurses, the leaflets were supporting. This should enable a quality improvement program to a sustainable NBS program in Flanders.

Metachromatic leukodystrophy: To screen or not to screen?

Metachromatic leukodystrophy (MLD) is a neurodegenerative lysosomal storage disorder caused by biallelic pathogenic variants in the gene encoding arylsulfatase A. Disease onset is variable (with late infantile, early and late juvenile, and adult forms) and treatment options depend on age and disease symptoms at onset. In the past, allo-hematopoietic stem cell transplantation (allo-HSCT) has been the best treatment option, following strict selection criteria. The outcome however is variable and morbidity remains high. This paved the way to the development of new treatment options, some of them aiming to be curative. In the light of this changing therapeutic field, newborn screening is becoming a valuable option. This narrative review aims to describe the outcome of allo-HSCT in the different MLD disease forms, and, in addition, reviews new treatment options. Finally, the shift of the field towards newborn screening for MLD is discussed.

Dihydropyrimidinase deficiency: Phenotype, genotype and structural consequences in 17 patients.

Dihydropyrimidinase (DHP) is the second enzyme of the pyrimidine degradation pathway and catalyses the ring opening of 5,6-dihydrouracil and 5,6-dihydrothymine. To date, only 11 individuals have been reported suffering from a complete DHP deficiency. Here, we report on the clinical, biochemical and molecular findings of 17 newly identified DHP deficient patients as well as the analysis of the mutations in a three-dimensional framework. Patients presented mainly with neurological and gastrointestinal abnormalities and markedly elevated levels of 5,6-dihydrouracil and 5,6-dihydrothymine in plasma, cerebrospinal fluid and urine. Analysis of DPYS, encoding DHP, showed nine missense mutations, two nonsense mutations, two deletions and one splice-site mutation. Seventy-one percent of the mutations were located at exons 5-8, representing 41% of the coding sequence. Heterologous expression of 11 mutant enzymes in Escherichia coli showed that all but two missense mutations yielded mutant DHP proteins without significant activity. Only DHP enzymes containing the mutations p.R302Q and p.T343A possessed a residual activity of 3.9% and 49%, respectively. The crystal structure of human DHP indicated that the point mutations p.R490C, p.R302Q and p.V364M affect the oligomerization of the enzyme. In contrast, p.M70T, p.D81G, p.L337P and p.T343A affect regions near the di-zinc centre and the substrate binding site. The p.S379R and p.L7V mutations were likely to cause structural destabilization and protein misfolding. Four mutations were identified in multiple unrelated DHP patients, indicating that DHP deficiency may be more common than anticipated.

Data mining methods for classification of Medium-Chain Acyl-CoA dehydrogenase deficiency (MCADD) using non-derivatized tandem MS neonatal screening data.

Newborn screening programs for severe metabolic disorders using tandem mass spectrometry are widely used. Medium-Chain Acyl-CoA dehydrogenase deficiency (MCADD) is the most prevalent mitochondrial fatty acid oxidation defect (1:15,000 newborns) and it has been proven that early detection of this metabolic disease decreases mortality and improves the outcome. In previous studies, data mining methods on derivatized tandem MS datasets have shown high classification accuracies. However, no machine learning methods currently have been applied to datasets based on non-derivatized screening methods. A dataset with 44,159 blood samples was collected using a non-derivatized screening method as part of a systematic newborn screening by the PCMA screening center (Belgium). Twelve MCADD cases were present in this partially MCADD-enriched dataset. We extended three data mining methods, namely C4.5 decision trees, logistic regression and ridge logistic regression, with a parameter and threshold optimization method and evaluated their applicability as a diagnostic support tool. Within a stratified cross-validation setting, a grid search was performed for each model for a wide range of model parameters, included variables and classification thresholds. The best performing model used ridge logistic regression and achieved a sensitivity of 100%, a specificity of 99.987% and a positive predictive value of 32% (recalibrated for a real population), obtained in a stratified cross-validation setting. These results were further validated on an independent test set. Using a method that combines ridge logistic regression with variable selection and threshold optimization, a significantly improved performance was achieved compared to the current state-of-the-art for derivatized data, while retaining more interpretability and requiring less variables. The results indicate the potential value of data mining methods as a diagnostic support tool.

Vertebral Tongue-Like Deformity in Mucopolysaccharidosis VI.

Teaching point: Defective development of the anterior portion of the vertebral body at the thoracolumbar junction may be an important imaging clue in the diagnosis of mucopolysaccharidosis.

Long-term efficacy and safety of sapropterin in patients who initiated sapropterin at < 4 years of age with phenylketonuria: results of the 3-year extension of the SPARK open-label, multicentre, randomised phase IIIb trial.

BACKGROUND: During the initial 26-week SPARK (Safety Paediatric efficAcy phaRmacokinetic with Kuvan®) study, addition of sapropterin dihydrochloride (Kuvan®; a synthetic formulation of the natural cofactor for phenylalanine hydroxylase, tetrahydrobiopterin; BH4), to a phenylalanine (Phe)-restricted diet, led to a significant improvement in Phe tolerance versus a Phe-restricted diet alone in patients aged 0-4 years with BH4-responsive phenylketonuria (PKU) or mild hyperphenylalaninaemia (HPA). Based on these results, the approved indication for sapropterin in Europe was expanded to include patients < 4 years of age. Herein, we present results of the SPARK extension study (NCT01376908), evaluating the long-term safety, dietary Phe tolerance, blood Phe concentrations and neurodevelopmental outcomes in patients < 4 years of age at randomisation, over an additional 36 months of treatment with sapropterin. RESULTS: All 51 patients who completed the 26-week SPARK study period entered the extension period. Patients who were previously treated with a Phe-restricted diet only ('sapropterin extension' group; n = 26), were initiated on sapropterin at 10 mg/kg/day, which could be increased up to 20 mg/kg/day. Patients previously treated with sapropterin plus Phe-restricted diet, remained on this regimen in the extension period ('sapropterin continuous' group; n = 25). Dietary Phe tolerance increased significantly at the end of the study versus baseline (week 0), by 38.7 mg/kg/day in the 'sapropterin continuous' group (95% CI 28.9, 48.6; p < 0.0001). In the 'sapropterin extension' group, a less pronounced effect was observed, with significant differences versus baseline (week 27) only observed between months 9 and 21; dietary Phe tolerance at the end of study increased by 5.5 mg/kg/day versus baseline (95% CI - 2.8, 13.8; p = 0.1929). Patients in both groups had normal neuromotor development and growth parameters. CONCLUSIONS: Long-term treatment with sapropterin plus a Phe-restricted diet in patients who initiated sapropterin at < 4 years of age with BH4-responsive PKU or mild HPA maintained improvements in dietary Phe tolerance over 3.5 years. These results continue to support the favourable risk/benefit profile for sapropterin in paediatric patients (< 4 years of age) with BH4-responsive PKU. Frequent monitoring of blood Phe levels and careful titration of dietary Phe intake to ensure adequate levels of protein intake is necessary to optimise the benefits of sapropterin treatment. Trial registration ClinicalTrials.gov, NCT01376908. Registered 17 June 2011, https://clinicaltrials.gov/ct2/show/NCT01376908 .

Belgian rare diseases plan in clinical pathology: identification of key biochemical diagnostic tests and establishment of reference laboratories and financing conditions.

BACKGROUND: One objective of the Belgian Rare Diseases plan is to improve patients' management using phenotypic tests and, more specifically, the access to those tests by identifying the biochemical analyses used for rare diseases, developing new financing conditions and establishing reference laboratories. METHODS: A feasibility study was performed from May 2015 until August 2016 in order to select the financeable biochemical analyses, and, among them, those that should be performed by reference laboratories. This selection was based on an inventory of analyses used for rare diseases and a survey addressed to the Belgian laboratories of clinical pathology (investigating the annual analytical costs, volumes, turnaround times and the tests unavailable in Belgium and outsourced abroad). A proposal of financeable analyses, financing modalities, reference laboratories' scope and budget estimation was developed and submitted to the Belgian healthcare authorities. After its approval in December 2016, the implementation phase took place from January 2017 until December 2019. RESULTS: In 2019, new reimbursement conditions have been published for 46 analyses and eighteen reference laboratories have been recognized. Collaborations have also been developed with 5 foreign laboratories in order to organize the outsourcing and financing of 9 analyses unavailable in Belgium. CONCLUSIONS: In the context of clinical pathology and rare diseases, this initiative enabled to identify unreimbursed analyses and to meet the most crucial financial needs. It also contributed to improve patients' management by establishing Belgian reference laboratories and foreign referral laboratories for highly-specific analyses and a permanent surveillance, quality and financing framework for those tests.

Belgian Fabry study: prevalence of Fabry disease in a cohort of 1000 young patients with cerebrovascular disease.

BACKGROUND AND PURPOSE: Data on the prevalence of Fabry disease in patients with central nervous system pathology are limited and controversial. In this study, we assessed the prevalence of Fabry disease in young patients presenting with cerebrovascular disease in Belgium. METHODS: In this national, prospective, multicenter study, we screened for Fabry disease in 1000 patients presenting with ischemic stroke, transient ischemic attack, or intracranial hemorrhage; unexplained white matter lesions; or vertebrobasilar dolichoectasia. In male patients, we measured alpha-galactosidase A (alpha-GAL A) activity in dried blood spots. Female patients were screened for mutations by exonic DNA sequencing of the alpha-GAL A gene. RESULTS: alpha-GAL A activity was deficient in 19 men (3.5%), although all had normal alpha-GAL A gene sequences. Enzymatic deficiency was confirmed on repeat assessment in 2 male patients (0.4%). We identified missense mutations in 8 unrelated female patients (1.8%): Asp313Tyr (n=5), Ala143Thr (n=2), and Ser126Gly (n=1). The pathogenicity of the 2 former missense mutations is controversial. Ser126Gly is a novel mutation that can be linked to late-onset Fabry disease. CONCLUSIONS: alpha-GAL A deficiency may play a role in up to 1% of young patients presenting with cerebrovascular disease. These findings suggest that atypical variants of Fabry disease with late-onset cerebrovascular disease exist, although the clinical relevance is unclear in all cases.

Placental Findings in Lysosomal Storage Disease Diagnosis: A Case Report of Galactosialidosis.

Introduction. Lysosomal storage disorders (LSDs) are rare diseases with more than 50 different entities described today. The spectrum of phenotypes varies from severe to lethal and early-onset disease to mild and late onset. Recognition of the clinical signs and diagnostic workup is challenging and requires expertise. Diagnosis relies on finding abnormal metabolites in urine and serum followed by further enzymatic or molecular analysis. Routine histological examination of the foetal and placental tissues frequently shows vacuolisation, providing a readily available important clue to the diagnosis. Case Report. A third child of consanguineal parents showed several dysmorphic features and a complicated neonatal period with eventual demise in the early postneonatal period due to respiratory failure. An LSD was suspected based on clinical presentation, urine metabolite excretion, skeletal radiograph, and vacuolisation in lymphocytes and placental tissues on, respectively, blood smear and routine histological examination. Homozygosity mapping favoured galactosialidosis. The diagnosis was confirmed by massive parallel sequencing, revealing a single nucleotide variation in the CTSA gene (c.265A>C, p.Ser89Arg). Discussion. Histological placental examination may be either the first clue or complimentary evidence in recognizing LSDs. It is important to recognize these clues as it may prompt further investigation and facilitate earlier recognition of the disease.

Dietary practices in methylmalonic acidaemia: a European survey.

Background The dietary management of methylmalonic acidaemia (MMA) is a low-protein diet providing sufficient energy to avoid catabolism and to limit production of methylmalonic acid. The goal is to achieve normal growth, good nutritional status and the maintenance of metabolic stability. Aim To describe the dietary management of patients with MMA across Europe. Methods A cross-sectional questionnaire was sent to European colleagues managing inherited metabolic disorders (IMDs) (n=53) with 27 questions about the nutritional management of organic acidaemias. Data were analysed by different age ranges (0-6 months; 7-12 months; 1-10 years; 11-16 years; >16 years). Results Questionnaires were returned from 53 centres. Twenty-five centres cared for 80 patients with MMA vitamin B12 responsive (MMAB12r) and 43 centres managed 215 patients with MMA vitamin B12 non-responsive (MMAB12nr). For MMAB12r patients, 44% of centres (n=11/25) prescribed natural protein below the World Health Organization/Food and Agriculture Organization/United Nations University (WHO/FAO/UNU) 2007 safe levels of protein intake in at least one age range. Precursor-free amino acids (PFAA) were prescribed by 40% of centres (10/25) caring for 36% (29/80) of all the patients. For MMAB12nr patients, 72% of centres (n=31/43) prescribed natural protein below the safe levels of protein intake (WHO/FAO/UNU 2007) in at least one age range. PFAA were prescribed by 77% of centres (n=33/43) managing 81% (n=174/215) of patients. In MMAB12nr patients, 90 (42%) required tube feeding: 25 via a nasogastric tube and 65 via a gastrostomy. Conclusions A high percentage of centres used PFAA in MMA patients together with a protein prescription that provided less than the safe levels of natural protein intake. However, there was inconsistent practices across Europe. Long-term efficacy studies are needed to study patient outcome when using PFAA with different severities of natural protein restrictions in patients with MMA to guide future practice.

Genotype-phenotype correlation in PEX5-deficient peroxisome biogenesis defective cell lines.

Proteins destined for the peroxisomal matrix are targeted by virtue of a peroxisomal targeting sequence type 1 (PTS1) or type 2 (PTS2). In humans, targeting of either class of proteins relies on a cytosolic receptor protein encoded by the PEX5 gene. Alternative splicing of PEX5 results in two protein variants, PEX5S and PEX5L. PEX5S is exclusively involved in PTS1 protein import, whereas PEX5L mediates the import of both PTS1 and PTS2 proteins. Genetic complementation testing with over 500 different fibroblast cell lines from patients diagnosed with a peroxisome biogenesis disorder (PBD) identified 11 cell lines with a defect in PEX5. The aim of this study was to characterize these cell lines at a biochemical and genetic level. To this end, the cultured fibroblasts were analyzed for very long chain fatty acid (VLCFA) concentrations, peroxisomal beta-and alpha-oxidation, dihydroxyacetone-phosphate acyltransferase (DHAPAT) activity, peroxisomal thiolase, and catalase immunofluorescence. Mutation analysis of the PEX5 gene revealed 11 different mutations, eight of which are novel. PTS1- and PTS2-protein import capacity was assessed by transfection of the cells with green fluorescent protein (GFP) tagged with either PTS1 or PTS2. Six cell lines showed a defect in both PTS1 and PTS2 protein import, whereas four cell lines only showed a defect in PTS1 protein import. The location of the different mutations within the PEX5 amino acid sequence correlates rather well with the peroxisomal protein import defect observed in the cell lines.

Mitochondrial mosaics in the liver of 3 infants with mtDNA defects.

BACKGROUND: In muscle cytochrome oxidase (COX) negative fibers (mitochondrial mosaics) have often been visualized. METHODS: COX activity staining of liver for light and electron microscopy, muscle stains, blue native gel electrophoresis and activity assays of respiratory chain proteins, their immunolocalisation, mitochondrial and nuclear DNA analysis. RESULTS: Three unrelated infants showed a mitochondrial mosaic in the liver after staining for COX activity, i.e. hepatocytes with strongly reactive mitochondria were found adjacent to cells with many negative, or barely reactive, mitochondria. Deficiency was most severe in the patient diagnosed with Pearson syndrome. Ragged-red fibers were absent in muscle biopsies of all patients. Enzyme biochemistry was not diagnostic in muscle, fibroblasts and lymphocytes. Blue native gel electrophoresis of liver tissue, but not of muscle, demonstrated a decreased activity of complex IV; in both muscle and liver subcomplexes of complex V were seen. Immunocytochemistry of complex IV confirmed the mosaic pattern in two livers, but not in fibroblasts. MRI of the brain revealed severe white matter cavitation in the Pearson case, but only slight cortical atrophy in the Alpers-Huttenlocher patient, and a normal image in the 3rd. MtDNA in leucocytes showed a common deletion in 50% of the mtDNA molecules of the Pearson patient. In the patient diagnosed with Alpers-Huttenlocher syndrome, mtDNA was depleted for 60% in muscle. In the 3rd patient muscular and hepatic mtDNA was depleted for more than 70%. Mutations in the nuclear encoded gene of POLG were subsequently found in both the 2nd and 3rd patients. CONCLUSION: Histoenzymatic COX staining of a liver biopsy is fast and yields crucial data about the pathogenesis; it indicates whether mtDNA should be assayed. Each time a mitochondrial disorder is suspected and muscle data are non-diagnostic, a liver biopsy should be recommended. Mosaics are probably more frequent than observed until now. A novel pathogenic mutation in POLG is reported.Tentative explanations for the mitochondrial mosaics are, in one patient, unequal partition of mutated mitochondria during mitoses, and in two others, an interaction between products of several genes required for mtDNA maintenance.

Phase I/II Trial of Liver-derived Mesenchymal Stem Cells in Pediatric Liver-based Metabolic Disorders: A Prospective, Open Label, Multicenter, Partially Randomized, Safety Study of One Cycle of Heterologous Human Adult Liver-derived Progenitor Cells (HepaStem) in Urea Cycle Disorders and Crigler-Najjar Syndrome Patients.

BACKGROUND: Regenerative medicine using stem cell technology is an emerging field that is currently tested for inborn and acquired liver diseases. OBJECTIVE: This phase I/II prospective, open label, multicenter, randomized trial aimed primarily at evaluating the safety of Heterologous Human Adult Liver-derived Progenitor Cells (HepaStem) in pediatric patients with urea cycle disorders (UCDs) or Crigler-Najjar (CN) syndrome 6 months posttransplantation. The secondary objective included the assessment of safety up to 12 months postinfusion and of preliminary efficacy. METHODS: Fourteen patients with UCDs and 6 with CN syndrome were divided into 3 cohorts by body weight and intraportally infused with 3 doses of HepaStem. Clinical status, portal vein hemodynamics, morphology of the liver, de novo detection of circulating anti-human leukocyte antigen antibodies, and clinically significant adverse events (AEs) and serious adverse events to infusion were evaluated by using an intent-to-treat analysis. RESULTS: The overall safety of HepaStem was confirmed. For the entire study period, patient-month incidence rate was 1.76 for the AEs and 0.21 for the serious adverse events, of which 38% occurred within 1 month postinfusion. There was a trend of higher events in UCD as compared with CN patients. Segmental left portal vein thrombosis occurred in 1 patient and intraluminal local transient thrombus in a second patient. The other AEs were in line with expectations for catheter placement, cell infusion, concomitant medications, age, and underlying diseases. CONCLUSIONS: This study led to European clinical trial authorization for a phase II study in a homogeneous patient cohort, with repeated infusions and intermediate doses.