Hematopoietic stem cell transplantation or enzyme replacement therapy in Gaucher disease type 3.

Gaucher disease (GD) is a lysosomal storage disorder with glucocerebroside accumulation in the macrophages. The disease is divided into three types based on neurocognitive involvement with GD1 having no involvement while the acute (GD2) and chronic (GD3) are neuronopathic. The non-neurological symptoms of GD3 are well treated with enzyme replacement therapy (ERT) which has replaced hematopoietic stem cell transplantation (HSCT). ERT is unable to prevent neurological progression as the enzyme cannot cross the blood-brain barrier. In this retrospective study, we report the general, neurocognitive, and biochemical outcomes of three siblings with GD3 after treatment with ERT or HSCT. Two were treated with HSCT (named HSCT1 and HSCT2) and one with ERT (ERT1). All patients were homozygous for the c.1448 T > C, (p.Leu483Pro) variant in the GBA1 gene associated with GD3. ERT1 experienced neurocognitive progression with development of seizures, oculomotor apraxia, perceptive hearing loss and mental retardation. HSCT1 had no neurological manifestations, while HSCT2 developed perceptive hearing loss and low IQ. Chitotriosidase concentrations were normal in plasma and cerebrospinal fluid (CSF) for HSCT1 and HSCT2, but both were markedly elevated in ERT1. We report a better neurological outcome and a normalization of chitotriosidase in the two siblings treated with HSCT compared to the ERT-treated sibling. With the advancements in HSCT over the past 25 years, we may reconsider using HSCT in GD3 to achieve a better neurological outcome and limit disease progression.

The impact of phenylalanine levels during pregnancy on birth weight and later development in children born to women with phenylketonuria.

Strict metabolic control with dietary treatment during pregnancy is essential for women with phenylketonuria (PKU), as elevated levels of phenylalanine (Phe) are toxic to the developing fetus. Maternal delay in achievement of the recommended Phe level during pregnancy is associated with delayed development of the child. However, the extent to which risk is changed by later or less stringently performed dietary treatment is unclear. The aim of this study was to investigate the impact of Phe levels and time of initiation of a Phe-restricted diet in pregnant women with PKU on birth weight, head circumference and later development of their children. Birth data were obtained from the medical records of women with PKU giving birth in the period 1980-2020. Later development was investigated by interviewing the mothers about their children's development and health. We included 79 children of 41 women with PKU. The women showed good adherence with the diet and had mean blood Phe levels within target range (248 ± 62 µmol/L). The children's development was not affected by fluctuations in the women's Phe levels, that occurred especially in first trimester. Despite maternal Phe levels being within target range, 19 children (26.8%) had low birth weight below 10th percentile. This study indicates that with dietary treatment, the children are born with the same prospect for normal development and health as children born to non-PKU mothers. This is despite maternal fluctuations in the Phe levels during first trimester.

Influence of early identification and therapy on long-term outcomes in early-onset MTHFR deficiency.

MTHFR deficiency is a severe inborn error of metabolism leading to impairment of the remethylation of homocysteine to methionine. Neonatal and early-onset patients mostly exhibit a life-threatening acute neurologic deterioration. Furthermore, data on early-onset patients' long-term outcomes are scarce. The aims of this study were (1) to study and describe the clinical and laboratory parameters of early-onset MTHFR-deficient patients (i.e., ≤3 months of age) and (2) to identify predictive factors for severe neurodevelopmental outcomes in a cohort with early and late onset MTHFR-deficient patients. To this end, we conducted a retrospective, multicentric, international cohort study on 72 patients with MTHFR deficiency from 32 international metabolic centres. Characteristics of the 32 patients with early-onset MTHFR deficiency were described at time of diagnosis and at the last follow-up visit. Logistic regression analysis was used to identify predictive factors of severe neurodevelopmental outcome in a broader set of patients with early and non-early-onset MTHFR deficiency. The majority of early-onset MTHFR-deficient patients (n = 32) exhibited neurologic symptoms (76%) and feeding difficulties (70%) at time of diagnosis. At the last follow-up visit (median follow-up time of 8.1 years), 76% of treated early-onset patients (n = 29) exhibited a severe neurodevelopmental outcome. Among the whole study population of 64 patients, pre-symptomatic diagnosis was independently associated with a significantly better neurodevelopmental outcome (adjusted OR 0.004, [0.002-0.232]; p = 0.003). This study provides evidence for benefits of pre-symptomatic diagnosis and appropriate therapeutic management, highlighting the need for systematic newborn screening for MTHFR deficiency and pre-symptomatic treatment that may improve outcome.

Compound heterozygous mutations in two different domains of ALDH18A1 do not affect the amino acid levels in a patient with hereditary spastic paraplegia.

Mutations in ALDH18A1 can cause autosomal recessive and dominant hereditary spastic paraplegia and autosomal recessive and dominant cutis laxa. ALDH18A1 encodes delta-1-pyrroline-5-carboxylate synthetase (P5CS), which consists of two domains, the glutamate 5-kinase (G5K) and the gamma-glutamyl phosphate reductase (GR5P) domain. The location of the mutations in the gene has influence on whether the amino acid levels are affected. Mutations affecting the G5K domain have previously been found to cause reduced plasma levels of proline, citrulline and arginine, whereas such effect is not seen with mutations affecting the GR5P domain. We present a 19-year old male patient with autosomal recessive spastic paraplegia and compound heterozygosity for two ALDH18A1 mutations, one in each of the P5CS domains. This young man has spastic paraplegia with onset in childhood and temporal lobe epilepsy, but normal levels of proline, ornithine and arginine. To our knowledge, this is the first case with compound heterozygous mutations affecting both P5CS domains, where levels of plasma amino acids have been reported.

Cryopreservation of ovarian tissue may be considered in young girls with galactosemia.

PURPOSE: The aim was to describe the first experience with fertility preservation by cryopreservation of ovarian tissue (OTC) in pre-pubertal girls with galactosemia and further to characterize ovarian follicular morphology and expression of proteins important for ovarian function. METHODS: Retrospectively, follicle density was estimated in ovarian cortical tissues from 6 pre-pubertal girls below the age of 12 years diagnosed with galactosemia and from 31 girls below the age of 18 years who had one ovary removed for fertility preservation for other reasons prior to gonadotoxic treatment. Additionally, expression of 4 glycoproteins important for follicle development were analyzed with immunohistochemistry in two galactosemic ovaries (aged 0.9 and 1.7 years) and compared to normal age-matched controls. The proteins included were: anti-Müllerian hormone (AMH) pro-mature and C-terminal, growth differentiation factor-9 (GDF-9), bone morphogenetic protein 15 (BMP-15), and pregnancy-associated plasma protein A (PAPP-A). RESULTS: Girls with galactosemia below the age of 5 years presented with morphological normal follicles and follicle densities within the 95% confidence interval (CI) of controls. No follicles were detected in the ovary from an 11.7-year-old girl with galactosemia. Expression of AMH, GDF-9, BMP-15, and PAPP-A appeared similar in follicles from girls with galactosemia and controls. CONCLUSIONS: These findings suggest that young girls with galactosemia maintain follicles in early childhood and fertility cryopreservation may be considered an option in this patient group. The pathophysiology of galactosemia leading to an accelerated follicle loss is unknown and it is currently unknown to what extent transplanted ovarian tissue can sustain fertility in adult life.

Alpha-mannosidosis - a review of genetic, clinical findings and options of treatment.

Alpha-mannosidosis (OMIM 248500) is a rare, autosomal recessive, multisystemic, progressive lysosomal storage disorder caused by a deficiency of alpha-mannosidase. It has been described in humans, cattle, domestic cats, mice and guinea pigs. In humans, alpha-mannosidosis results in progressive facial- and skeletal abnormalities, motor impairment, hearing impairment, intellectual disability, recurrent infections and immune deficiency. This review provides detailed information regarding the variability of manifestations and a description of current treatment and treatment under investigation for alpha-mannosidosis. The pathology, genetics and clinical pictures, including impairments in the activity of daily living are discussed.

Relationship between MAN2B1 genotype/subcellular localization subgroups, antidrug antibody detection, and long-term velmanase alfa treatment outcomes in patients with alpha-mannosidosis.

Alpha-mannosidosis (AM), an autosomal recessive disorder caused by pathogenic biallelic variants in the MAN2B1 gene, leads to lysosomal alpha-mannosidase deficiency and accumulation of mannose-rich oligosaccharides. Velmanase alfa (VA), a recombinant human lysosomal alpha-mannosidase, is the first enzyme replacement therapy for non-neurological symptoms of AM. Previously, a potential relationship was identified between three MAN2B1 genotype/subcellular localization subgroups (G1, G2, and G3) and AM disease severity. In VA-treated patients with AM, it is unknown if a relationship exists between MAN2B1 genotype/subcellular localization subgroups, antidrug antibodies (ADAs), and infusion-related reactions (IRRs). This pooled analysis evaluated data from 33 VA-treated patients with AM to investigate this relationship. Overall, 10 patients were positive for ADAs, 4 of whom had treatment-emergent ADAs (G1: 3/7 [43%]; G2: 1/17 [6%]; G3: 0/9). Treatment-emergent ADA-positive patients with relatively high titers (n = 2; G1: 1012 U/ml and G2: 440 U/ml) experienced mild/moderate IRRs that were well-managed; patients with lower titers (n = 2) experienced no IRRs. Overall, changes from baseline in serum oligosaccharides and immunoglobulin G levels did not vary between ADA-positive and ADA-negative patients, suggesting a similar effect of VA treatment regardless of ADA status in most patients. Clinical outcomes (3MSCT and 6MWT) were also similar in most patients regardless of ADA status. While further studies are needed, these data suggest a relationship between MAN2B1 genotype/subcellular localization subgroups and ADA development, with G1 and G2 subgroups more likely to develop ADAs and IRRs. Regardless, this study suggests that ADAs have limited effect on the clinical impact of VA in most patients with AM.

Adult patient diagnosed with NADSYN1 associated congenital NAD deficiency and analysis of NAD levels to be published in: European Journal of Medical Genetics.

INTRODUCTION: Nicotinamide adenine dinucleotide (NAD) is an essential cosubstrate/coenzyme in multiple cellular redox processes and a substrate in several non-redox reactions. NADSYN1 encodes NAD synthetase 1, an enzyme in the NAD de novo synthesis pathway and the Preiss-Handler pathway, and biallelic pathogenic variants causes NAD deficiency associated with vertebral, cardiac, renal and limb defects. Szot et al. and Kortbawi et al. have reported a total of seven patients with NADSYN1 associated congenital NAD deficiency disorder with the oldest patient being seven years old. PATIENT DATA: We present a male patient age 30 with a height of 130 cm and numerous skeletal malformations including segmentation defects of the spine, rib anomalies and unequal leg length as well as bilateral ptosis, cleft palate and asymmetric dysmorphic facial features. The patient underwent surgery for an aortic stenosis due to a bicuspid valve. No malformations of the kidneys or urinary tract were identified. RESULTS: Trio exome sequencing revealed a homozygous missense variant in NADSYN1 c.1717G > A (p.Ala573Thr). Both parents were unaffected carriers of the variant. Analysis of NAD levels showed that the patient had a lower NAD pool compared to his unaffected siblings. The NAD pool rose approximately 25% after supplementation with nicotinamide, a NAD precursor for the salvage pathway. CONCLUSION: The variant was previously reported in four patients and functional analyses by Szot et al. support the pathogenicity of the variant. We report an adult patient with NADSYN1 associated congenital NAD deficiency disorder and expand the phenotypic spectrum. We also present analysis of the NAD levels before and after supplementation with nicotinamide.

MCAD deficiency in Denmark.

Medium-chain acyl-CoA dehydrogenase deficiency (MCADD) is the most common defect of fatty acid oxidation. Many countries have introduced newborn screening for MCADD, because characteristic acylcarnitines can easily be identified in filter paper blood spot samples by tandem mass spectrometry (MS/MS), because MCADD is a frequent disease, and because of the success of early treatment initiated before clinical symptoms have emerged. In Denmark we have screened 519,350 newborns for MCADD by MS/MS and identified 58 affected babies. The diagnosis of MCADD was confirmed in all 58 newborns by mutation analysis. This gives an incidence of MCADD detected by newborn screening in Denmark of 1/8954. In sharp contrast to this we found that the incidence of clinically presenting MCADD in Denmark in the 10 year period preceding introduction of MS/MS-based screening was only 1 in 39,691. This means that four times more newborns with MCADD are detected by screening than what is expected based on the number of children presenting clinically in an unscreened population. The mutation spectrum in the newborns detected by screening is different from that observed in clinically presenting patients with a much lower proportion of newborns being homozygous for the prevalent disease-causing c.985A>G mutation. A significant number of the newborns have genotypes with mutations that have not been observed in patients detected clinically. Some of these mutations, like c.199T>C and c.127G>A, are always associated with a milder biochemical phenotype and may cause a milder form of MCADD with a relatively low risk of disease manifestation, thereby explaining part of the discrepancy between the frequency of clinically manifested MCADD and the frequency of MCADD determined by screening. In addition, our data suggest that some of this discrepancy can be explained by a reduced penetrance of the c.985A>G mutation, with perhaps only 50% of c.985A>G homozygotes presenting with disease manifestations. Interestingly, we also report that the observed number of newborns identified by screening who are homozygous for the c.985A>G mutation is twice that predicted from the estimated carrier frequency. We therefore redetermined the carrier frequency in a new sample of 1946 blood spots using a new assay, but this only confirmed that the c.985A>G carrier frequency in Denmark is approximately 1/105. We conclude that MCADD is much more frequent than expected, has a reduced penetrance and that rapid genotyping using the initial blood spot sample is important for correct diagnosis and counseling.

Biochemical screening of 504,049 newborns in Denmark, the Faroe Islands and Greenland--experience and development of a routine program for expanded newborn screening.

Expanded newborn screening for selected inborn errors of metabolism (IEM) in Denmark, the Faroe Islands and Greenland was introduced in 2002. We now present clinical, biochemical, and statistical results of expanded screening (excluding PKU) of 504,049 newborns during nine years as well as diagnoses and clinical findings in 82,930 unscreened newborns born in the same period. The frequencies of diagnoses made within the panel of disorders screened for are compared with the frequencies of the disorders in the decade preceding expanded newborn screening. The expanded screening was performed as a pilot study during the first seven years, and the experience obtained during these years was used in the development of the routine neonatal screening program introduced in 2009. Methods for screening included tandem mass spectrometry and an assay for determination of biotinidase activity. A total of 310 samples from 504,049 newborns gave positive screening results. Of the 310 results, 114 were true positive, including results from 12 newborns in which the disease in question was subsequently diagnosed in their mothers. Thus, the overall frequency of an IEM in the screening panel was 1:4942 (mothers excluded) or 1:4421 (mothers included). The false positive rate was 0.038% and positive predictive value 37%. Overall specificity was 99.99%. All patients with true positive results were followed in The Center for Inherited Metabolic Disorders in Copenhagen, and the mean follow-up period was 45 months (range 2109 months). There were no deaths among the 102 children, and 94% had no clinically significant sequelae at last follow-up. Our study confirms the higher frequency of selected IEM after implementation of expanded newborn screening and suggests an improved outcome for several disorders. We argue that newborn screening for these disorders should be standard of care, though unresolved issues remain, e.g. about newborns with a potential for remaining asymptomatic throughout life. Well organized logistics of the screening program from screening laboratory to centralized, clinical management is important.

Use of Molecular Genetic Analyses in Danish Routine Newborn Screening.

Historically, the analyses used for newborn screening (NBS) were biochemical, but increasingly, molecular genetic analyses are being introduced in the workflow. We describe the application of molecular genetic analyses in the Danish NBS programme and show that second-tier molecular genetic testing is useful to reduce the false positive rate while simultaneously providing information about the precise molecular genetic variant and thus informing therapeutic strategy and easing providing information to parents. When molecular genetic analyses are applied as second-tier testing, valuable functional data from biochemical methods are available and in our view, such targeted NGS technology should be implemented when possible in the NBS workflow. First-tier NGS technology may be a promising future possibility for disorders without a reliable biomarker and as a general approach to increase the adaptability of NBS for a broader range of genetic diseases, which is important in the current landscape of quickly evolving new therapeutic possibilities. However, studies on feasibility, sensitivity, and specificity are needed as well as more insight into what views the general population has towards using genetic analyses in NBS. This may be sensitive to some and could have potentially negative consequences for the NBS programme.

Clinical and biochemical monitoring of patients with fatty acid oxidation disorders.

Evidence-based guidelines for monitoring patients with disorders in fatty acid oxidation (FAO) are lacking, and most protocols are based on expert statements. Here, we describe our protocol for Danish patients. Clinical monitoring is the most important measure and has the main aims of checking growth, development and diet and of bringing families to the clinic regularly to remind them of their child's risk and review how they cope and adjust, e.g. to an acute intercurrent illness. Most of these measures are simple and can be carried out during a routine out-patient visit; we seldom do more complicated assessments by a neuropsychologist, speech therapist, or physical and occupational therapists. Paraclinical measurements are not used for short-chain and medium-chain disorders; electrocardiography (including 24 h monitoring) and echocardiography are done for most patients with long-chain and carnitine transporter deficiencies. Eye examination is done in all, and liver ultrasonography in some patients with long-chain 3-hydroxyacyl-coenzyme A dehydrogenase/tri-functional protein (LCHAD/TFP) deficiencies. Biochemical follow-up includes determination of free carnitine and acylcarnitines. Free carnitine is measured to monitor carnitine supplementation in patients with multiple acyl-coenzyme A dehydrogenase deficiency (MADD) and carnitine transporter deficiency (CTD) and to follow metabolic control and disclose deficiency states in other FAO disorders. We are evaluating long-chain acylcarnitines in patients with long-chain disorders; so far there does not seem to be any clear-cut benefit in following these levels. An erythrocyte fatty acid profile is done in patients with long-chain disorders to test for essential fatty acid and docosahexanoic acid (DHA) deficiencies. The measurement of creatine kinase is helpful in long-chain disorders. Ongoing follow-up and education of the patient is important throughout life to prevent disease morbidity or death from metabolic crises.

[Treatment of monogenic disorders with viral transduced haematopoietic stem cells].

Infusion of ex vivo transduced haematopoietic stem cells (HSC) has emerged as a promising new treatment of certain monogenetic disorders. Since early clinical studies on patients with severe combined immune deficiency were halted due to de novo leukaemia, the technology has matured. Thus, treatment of transfusion-dependent thalassaemia and adenosine deaminase deficient severe combined immunodeficiency by using lentiviral vectors for gene correction of autologous HSC can induce expression of the deficient protein and thus potentially cure the patients. The review summarises recent advances allowing for clinical implementation of the treatment in Denmark.

Impaired Fat Oxidation During Exercise in Long-Chain Acyl-CoA Dehydrogenase Deficiency Patients and Effect of IV-Glucose.

CONTEXT: Long-chain 3-hydroxyacyl-coenzyme A dehydrogenase deficiency (LCHADD) affects oxidation of long-chain fatty acids (FAO) and is associated with risk of metabolic crises and episodic rhabdomyolysis. CASE DESCRIPTION: We present the cases of two patients with LCHADD. Patient 1 (male, 26 years old) was severely affected by muscle weakness and neuropathy. He was diagnosed at age 20 years and was nonadherent to standard dietary management. MRI revealed significant fat replacement of muscle in both calves. Patient 2 (female, 15 years old) was diagnosed at age 1 year. She had no muscle weakness and was compliant with the recommended diet. Compared with healthy persons, both patients had reduced FAO and palmitate oxidation, measured with indirect calorimetry and stable isotope technique during a submaximal cycle ergometer test. Patient 2 had some residual capacity to increase FAO and a compensatory higher carbohydrate oxidation, which ensured a near-normal exercise capacity. Patient 1 was unable to increase FAO and could only complete 23 minutes of exercise, vs 60 minutes by patient 2 and healthy persons. In both, 10% IV infusion of glucose (IV-glucose) during exercise increased carbohydrate oxidation slightly, but endurance was not improved, which likely relates to the fixed weakness in patient 1 and because the residual FAO was suppressed by the glucose infusion in both. CONCLUSION: The two patients illustrate that FAO is impaired and carbohydrate oxidation is elevated during exercise in patients affected by LCHADD, compared with healthy persons, but IV-glucose has no beneficial effect on exercise tolerance in LCHADD.

The impact of consanguinity on the frequency of inborn errors of metabolism.

INTRODUCTION: We investigated the frequency of con-sanguinity among the parents to newborns with inborn errors of metabolism (IEM) diagnosed by neonatal screening. METHODS: Data were obtained from 15 years of national newborn screening for selected IEM with autosomal recessive mode of inheritance. Among the 838,675 newborns from Denmark, The Faroe Islands and Greenland, a total of 196 newborns had an IEM of whom 155 from Denmark were included in this study. These results were crosschecked against medical records. Information on consanguinity was extracted from medical records and obtained through telephone contact with the families. RESULTS: Among ethnic Danes, two cases of consanguinity were identified among 93 families (2.15%). Among ethnic minorities, there were 20 cases of consanguinity among a total of 33 families (60.6%). Consequently, consanguinity was 28.2 times more frequent among descendants of other geographic places of origin than Denmark. The frequency of consanguinity was high among children of Pakistani, Afghan, Turkish and Arab origin (71.4%). The overall frequency of IEM was 25.5 times higher among children of these ethnic groups than among ethnic Danish children (5.35:10,000 versus 0.21:10,000). The frequency of IEM was 30-fold and 50-fold higher among Pakistanis (6.5:10,000) and Afghans (10.6:10,000), respectively, compared with ethnic Danish children. CONCLUSIONS: The data indicate a strong association between consanguinity and IEM. These figures may be useful to health professionals providing antenatal, paediatric and clinical genetic services. FUNDING: none. TRIAL REGISTRATION: not relevant.

Simultaneous quantification of succinylacetone and nitisinone for therapeutic drug monitoring in the treatment of Tyrosinemia type 1.

We present a straightforward and robust method for simultaneous quantification of succinylacetone and nitisinone in plasma using LC-ESI-MS/MS. The method has been developed for routine therapeutic drug monitoring in hepatorenal tyrosinemia type 1 (HT1) patients undergoing nitisinone treatment. Previous methods are based on separate analyses of succinylacetone and nitisinone, often using the potentially harmful compound hydrazine for derivatization of the former. In the present procedure, succinylacetone is derivatized in a single-step using butanolic HCl. Analyte extraction and sample clean-up is carried out by simple protein precipitation. The linear range for both analytes is 0.1 up to 125µM, covering the vast majority of encountered levels in real-life samples. The sensitivity and limit of quantification allows measurement of succinylacetone in the therapeutical range for HT1 patients. Stability studies show that succinylacetone is highly sensitive to storage conditions, whereas nitisinone shows little to no degradation. Correct sample handling is therefore important for reliable results when monitoring succinylacetone concentrations.

The impact of consanguinity on the frequency of inborn errors of metabolism.

Inborn errors of metabolism (IEM) are a heterogeneous group of genetic disorders present in all ethnic groups. We investigated the frequency of consanguinity among parents of newborns with IEM diagnosed by neonatal screening. Data were obtained from 15 years of expanded newborn screening for selected IEM with autosomal recessive mode of inheritance, a national screening program of newborns covering the period from 2002 until April 2017. Among the 838,675 newborns from Denmark, the Faroe Islands and Greenland, a total of 196 newborns had an IEM of whom 155 from Denmark were included in this study. These results were crosschecked against medical records. Information on consanguinity was extracted from medical records and telephone contact with the families. Among ethnic Danes, two cases of consanguinity were identified in 93 families (2.15%). Among ethnic minorities there were 20 cases of consanguinity among 33 families (60.6%). Consequently, consanguinity was 28.2 times more frequent among descendants of other geographic place of origin than Denmark. The frequency of consanguinity was conspicuously high among children of Pakistani, Afghan, Turkish and Arab origin (71.4%). The overall frequency of IEM was 25.5 times higher among children of Pakistani, Turkish, Afghan and Arab origin compared to ethnic Danish children (5.35:10,000 v 0.21:10,000). The frequency of IEM was 30-fold and 50-fold higher among Pakistanis (6.5:10,000) and Afghans (10.6:10,000), respectively, compared to ethnic Danish children. The data indicate a strong association between consanguinity and IEM. These figures could be useful to health professionals providing antenatal, pediatric, and clinical genetic services.

L-Carnitine Improves Skeletal Muscle Fat Oxidation in Primary Carnitine Deficiency.

Context: Primary carnitine deficiency (PCD) is an inborn error of fatty acid metabolism. Patients with PCD are risk for sudden heart failure upon fasting or illness if they are not treated with daily l-carnitine. Objective: To investigate energy metabolism during exercise in patients with PCD with and without l-carnitine treatment. Design: Interventional study. Setting: Hospital exercise laboratories and department of cardiology. Participants: Eight adults with PCD who were homozygous for the c.95A>G (p.N32S) mutation and 10 healthy age- and sex-matched controls. Intervention: Four-day pause in l-carnitine treatment. Main outcome measures: Total fatty acid and palmitate oxidation rates during 1-hour submaximal cycle ergometer exercise assessed with stable isotope method (U13C-palmitate and 2H2-d-glucose) and indirect calorimetry with and without l-carnitine. Results: Total fatty acid oxidation rate was higher in patients with l-carnitine treatment during exercise than without treatment [12.3 (SD, 3.7) vs 8.5 (SD, 4.6) µmol × kg-1 × min-1; P = 0.008]. However, the fatty acid oxidation rate was still lower in patients treated with l-carnitine than in the healthy controls [29.5 (SD, 10.1) µmol × kg-1 × min-1; P < 0.001] and in the l-carnitine group without treatment it was less than one third of that in the healthy controls (P < 0.001). In line with this, the palmitate oxidation rates during exercise were lower in the no-treatment period [144 (SD, 66) µmol × kg-1 × min-1] than during treatment [204 (SD, 84) µmol × kg-1 × min-1; P = 0.004) . Conclusions: The results indicate that patients with PCD have limited fat oxidation during exercise. l-Carnitine treatment in asymptomatic patients with PCD may not only prevent cardiac complications but also boost skeletal muscle fat metabolism during exercise.

Treatment outcome of twenty-two patients with guanidinoacetate methyltransferase deficiency: An international retrospective cohort study.

PURPOSE: Guanidinoacetate methyltransferase (GAMT) deficiency is an autosomal recessive disorder caused by pathogenic variants in GAMT. Brain creatine depletion and guanidinoacetate accumulation cause developmental delay, seizures and movement disorder. Treatment consists of creatine, ornithine and arginine-restricted diet. We initiated an international treatment registry using Research Electronic Data Capture (REDCap) software to evaluate treatment outcome. METHODS: Physicians completed an online REDCap questionnaire. Clinical severity score applied pre-treatment and on treatment. RESULTS: There were 22 patients. All had developmental delay, 18 had seizures and 8 had movement disorder. Based on the clinical severity score, 5 patients had a severe, 14 patients had a moderate and 3 patients had a mild phenotype. All patients had pathogenic variants in GAMT. The phenotype ranged from mild to moderate in patients with the most common c.327G > A variant. The phenotype ranged from mild to severe in patients with truncating variants. All patients were on creatine, 18 patients were on ornithine and 15 patients were on arginine- or protein-restricted diet. Clinical severity score improved in 13 patients on treatment. Developmental delay improved in five patients. One patient achieved normal development. Eleven patients became seizure free. Movement disorder resolved in four patients. CONCLUSION: In our small patient cohort, there seems to be no phenotype-genotype correlation. Creatine and ornithine and/or arginine- or protein-restricted diet were the most useful treatment to improve phenotype.

Prevalence of Mucopolysaccharidosis Types I, II, and VI in the Pediatric and Adult Population with Carpal Tunnel Syndrome (CTS). Retrospective and Prospective Analysis of Patients Treated for CTS.

BACKGROUND: We wanted to investigate whether the prevalence of mucopolysaccharidoses (MPS) I, II, and VI was higher than expected in a selected cohort of patients with carpal tunnel syndrome (CTS). CTS is a common finding in patients with MPS, and therefore we screened patients who had undergone surgery for CTS for undiagnosed MPS. PATIENTS AND METHODS: Patients who had been operated for CTS were found in databases from two hospitals. Furthermore, patients who had undergone surgery for CTS when under the age of 18 were retrieved from the National Patient Registry. All included patients had a filter paper blood spot sample taken that was subsequently analyzed enzymatically for MPS I, II, and VI. RESULTS: 425 patients were included. 402 patients tested negative in the first test. 23 had inconclusive result whereof 18 was negative in a second test. The remaining five patients had two inconclusive tests each and were referred for further examination at the Center for Inherited Metabolic Diseases where the diagnosis was excluded. Thus, all included patients were negative for both MPS I, II and VI. DISCUSSION/CONCLUSION: Though our sample size is relatively small, results indicate that MPS is not prevalent in a cohort of adult patients with monosymptomatic CTS, and that screening is not indicated in this setting.