Enzyme Deficiency Research Articles

A Patient Diagnosed with Li-Campeau Syndrome and Biotinidase Deficiency

Biotinidase (BTD) enzyme deficiency is a congenital metabolic disorder with autosomal recessive inheritance. Main symptoms in its deficiency are nervous system and skin manifestations. A 15-month-old patient who was diagnosed with Li-Campeau syndrome, was also diagnosed with BTD deficiency and his clinic rapidly improved with biotin treatment. With the awareness of different clinical presentations of BTD deficiency, patients presenting with clinical symptoms raising the suspicion of this disorder must be evaluated for enzyme activity and genetic analysis must be planned. It is of great importance to keep in mind the possibility of this rare but treatable neurometabolic disorder, even in countries with neonatal screening programme and include it in differential diagnoses in order to prevent irreversible symptoms.

A Patient Diagnosed with Li-Campeau Syndrome and Biotinidase Deficiency

Biotinidase (BTD) enzyme deficiency is a congenital metabolic disorder with autosomal recessive inheritance. Main symptoms in its deficiency are nervous system and skin manifestations. A 15-month-old patient who was diagnosed with Li-Campeau syndrome, was also diagnosed with BTD deficiency and his clinic rapidly improved with biotin treatment. With the awareness of different clinical presentations of BTD deficiency, patients presenting with clinical symptoms raising the suspicion of this disorder must be evaluated for enzyme activity and genetic analysis must be planned. It is of great importance to keep in mind the possibility of this rare but treatable neurometabolic disorder, even in countries with neonatal screening programme and include it in differential diagnoses in order to prevent irreversible symptoms.

Clinical Features and Laboratory Diagnosis of Aminoacidopathies: A Narrative Review

Context: There are severe and rare groups of genetic disorders due to defects in metabolic pathways, and they are generally called inborn errors of metabolism. Amino acids, as the building blocks of proteins, have many important structural and functional roles in the human body. The deficiencies of functional enzymes cause defects in metabolic pathways and lead to aminoacidopathies. The diagnosis of aminoacidopathies is challenging for most physicians, as they can present with multiple overlapping symptoms. Evidence Acquisition: PubMed, Cochrane, Embase, and CINAHL were searched with MeSH terms: ‘inborn errors of metabolism' OR ‘Metabolism, Inborn Errors' (MeSH) AND ‘Humans' (MeSH) AND 'Amino Acids/therapeutic use'(MeSH) AND ‘Newborn, Child' (MeSH) OR ‘child' OR ‘newborn' AND "Neonatal Screening"(MeSH). Results: This study summarized some important issues, including clinical and laboratory diagnoses of phenylketonuria, tyrosinemia, methionine, homocysteine and cysteine, sulfite oxidase deficiency, molybdenum cofactor deficiency, tryptophan, glycine, hyperoxaluria, creatine deficiency disorders, serine, proline, glutamine, and urea cycle defect. Conclusions: The prognosis of many metabolic disorders has improved due to recent advances in diagnosis and treatment. The biochemical knowledge of clinicians should be improved to comprehend metabolic disorders. As the diagnostic methods are based on organic acids in urine and acylcarnitine profile, it is necessary to enhance biochemistry knowledge to understand the logic.

Incidence of Bloodstream Infections after Hematopoietic Stem Cell Transplantation for Hurler Syndrome

Mucopolysaccharidosis type I (MPS I) is a rare genetic disorder characterized by the deficiency of the alpha-L-iduronidase enzyme necessary for the degradation of glycosaminoglycans (GAG) in the lysosome. Hurler syndrome is the most severe form of MPS I, manifesting as multiorgan dysfunction, cognitive delay, and death, usually within ten years if left untreated. Hematopoietic stem cell transplantation (HSCT) is the optimal treatment option, providing a permanent solution to enzyme deficiency and halting cognitive decline; however, the HSCT complications transplantation-associated thrombotic microangiopathy (TA-TMA) and graft-versus-host disease (GVHD) are known risk factors for bloodstream infection (BSI). BSI is a serious complication of HSCT, contributing to poor outcomes and transplantation-related morbidity. There are little data evaluating BSI after HSCT in the Hurler syndrome population. We performed a retrospective analysis of patients with Hurler syndrome who underwent HSCT at our center between 2013 and 2020 to determine the incidence of BSI within the first year post-transplantation. Patient BSI data were collected through the first year post-HSCT. Variables including patient demographics and transplantation-related characteristics were collected, including information on BSI and mortality. Twenty-five patients with a total of 28 HSCTs were included in the analysis; the majority (n=17; 68%) were male, with a median age of 1.1 years (interquartile range, .35 to 1.44 years) at the time of transplantation. The most common graft source was cord blood (n=15; 54%), followed by bone marrow (n=13; 46%), with the majority from matched unrelated donors (n=14; 52%) and mismatched unrelated donors (n=13; 44%). Sixteen BSIs were diagnosed in 12 patients (48%). Most infections (n=7; 43.8%) were diagnosed in the first 20 days post-transplantation, with fewer infections observed at later time points. Seven of the 9 Hurler patients diagnosed with TA-TMA (78%) also had a BSI. The incidence rate of BSIs in Hurler patients (n=12; 48%) was higher than the rates reported in the general pediatric HSCT population at 1-year post-transplantation (15% to 35%). Given the high rate of both TA-TMA and a BSI in Hurler patients, we suspect a possible correlation between the 2. Additionally, due to the time it takes for GAG levels to normalize post-HSCT in Hurler patients, it is reasonable to suspect that the high BSI rates in these patients are linked to their Hurler diagnosis. These findings bring awareness to possible disease-related factors contributing to high BSI rates in the Hurler population post-HSCT.

Effects of arginine on coenzyme-Q10 micelle uptake for mitochondria-targeted nanotherapy in phenylketonuria.

Phenylketonuria (PKU) is a rare inherited metabolic disease characterized by phenylalanine hydroxylase enzyme deficiency. In PKU patients, coenzyme Q10 (CoQ10) levels were found low. Therefore, we focused on the modification of CoQ10 to load the micelles and increase entry of micelles into the cell and mitochondria, and it is taking a part in ATP turnover. Micelles had produced by comparing two different production methods (thin-film layer and direct-dissolution), and characterization studies were performed (zeta potential, size, and encapsulation efficiency). Then, L-arginine (LARG) and poly-arginine (PARG) were incorporated with the micelles for subsequential release and PKU cell studies. The effects of these components on intracellular uptake and their use in the cellular cycle were analyzed by ELISA, Western blot, membrane potential measurement, and flow cytometry methods. In addition, both effects of LARG and PARG micelles on pharmacokinetics at the cellular level and their cell binding rate were determined. The thin-film method was found superior in micelle preparation. PARG/LARG-modified micelles showed sustained release. In the cellular and mitochondrial uptake of CoQ10, CoQ10-micelle + PARG > CoQ10-micelle + LARG > CoQ10-micelle > CoQ10 was found. This increased localization caused lowering of oxygen consumption rates, but maintaining mitochondrial membrane potential. The study results had showed that besides micelle formulation, PARG and LARG are effective in cellular and mitochondrial targeting.

Advanced CMR Techniques in Anderson-Fabry Disease: State of the Art.

Anderson-Fabry disease (AFD) is a rare multisystem X-linked lysosomal storage disorder caused by α-galactosidase A enzyme deficiency. Long-term cardiac involvement in AFD results in left ventricular hypertrophy and myocardial fibrosis, inducing several complications, mainly arrhythmias, valvular dysfunction, and coronary artery disease. Cardiac magnetic resonance (CMR) represents the predominant noninvasive imaging modality for the assessment of cardiac involvement in the AFD, being able to comprehensively assess cardiac regional anatomy, ventricular function as well as to provide tissue characterization. This review aims to explore the role of the most advanced CMR techniques, such as myocardial strain, T1 and T2 mapping, perfusion and hybrid imaging, as diagnostic and prognostic biomarkers.

Genetics of enzymatic dysfunctions in metabolic disorders and cancer.

Inherited metabolic disorders arise from mutations in genes involved in the biogenesis, assembly, or activity of metabolic enzymes, leading to enzymatic deficiency and severe metabolic impairments. Metabolic enzymes are essential for the normal functioning of cells and are involved in the production of amino acids, fatty acids and nucleotides, which are essential for cell growth, division and survival. When the activity of metabolic enzymes is disrupted due to mutations or changes in expression levels, it can result in various metabolic disorders that have also been linked to cancer development. However, there remains much to learn regarding the relationship between the dysregulation of metabolic enzymes and metabolic adaptations in cancer cells. In this review, we explore how dysregulated metabolism due to the alteration or change of metabolic enzymes in cancer cells plays a crucial role in tumor development, progression, metastasis and drug resistance. In addition, these changes in metabolism provide cancer cells with a number of advantages, including increased proliferation, resistance to apoptosis and the ability to evade the immune system. The tumor microenvironment, genetic context, and different signaling pathways further influence this interplay between cancer and metabolism. This review aims to explore how the dysregulation of metabolic enzymes in specific pathways, including the urea cycle, glycogen storage, lysosome storage, fatty acid oxidation, and mitochondrial respiration, contributes to the development of metabolic disorders and cancer. Additionally, the review seeks to shed light on why these enzymes represent crucial potential therapeutic targets and biomarkers in various cancer types.

Population Pharmacokinetic Modeling and Determination of Individual Exposure to Avalglucosidase Alfa in Adolescent and Adult Patients With Late-Onset Pompe Disease: Analysis of Pooled Data From Phase I to III Clinical Trials.

Pompe disease is a rare genetic disorder caused by a deficiency of a lysosomal enzyme called acid alpha-glucosidase and is classified into infantile and late-onset forms. Since 2006, an enzyme replacement therapy involving alglucosidase alfa has been available. In 2021, a new enzyme replacement therapy involving avalglucosidase alfa demonstrated improved clinical benefits. In this article, the authors describe the pharmacokinetics of avalglucosidase alfa using a population pharmacokinetic approach. The population pharmacokinetic model was developed using a data set that included 75 patients and 2042 plasma drug concentrations determined through enzymatic activity assay from 3 studies (phases I/II and III) and involved 3 dose levels (5, 10, and 20 mg/kg). The analysis was performed using NONMEM software. Two sequences were observed in the plasma drug concentration profile: the first kinetic driving exposure, and after 12 hours postdose, a slight rebound addressing very low concentrations that lasted up to 2 weeks. Following model screening, a model with a central compartment with parallel linear and nonlinear elimination and 2 concatenated peripheral compartments was proposed. A putative back-redistribution of a marginal fraction of the drug from the second peripheral compartment to the central compartment may explain the slight rebound in concentration. The final model's mean bias and precision for individual predictions were -2.66% and 30.7%, respectively, and -0.433% and 38.9%, respectively, for population predictions. A concatenated 3-compartment model was developed to describe the avalglucosidase alfa concentrations in patients with late-onset Pompe disease. None of the covariates tested could explain the interindividual variability.

Safety and Efficacy of Genistein in Sanfilippo Syndrome - A Systematic Review

Background: Sanfilippo syndrome, commonly known as mucopolysaccharidosis type III (MPS III), is a rare autosomal recessive lysosomal storage disease that primarily affects the brain and spinal cord. It is caused by a deficiency of enzymes involved in the catabolism of glycosaminoglycan (GAG) and heparin sulfate (HS). Although Genistein has been presented as a potential therapeutic, its safety and efficacy for the treatment of Sanfilippo syndrome are not well established. Objective: This systematic review aims to evaluate the safety and efficacy of Genistein with a primary endpoint of providing an inference whether the medication is producing any improvements when administered in patients suffering from Sanfilippo syndrome. Methods: An intensive computerized literature search was performed according to PRISMA guidelines in major databases such as PubMed, ScienceDirect, Embase, Science Citation Index Expanded, The Cochrane Library, and Web of Science until 30 April 2022. Studies evaluating the efficacy and safety of genistein in patients with Sanfilippo Syndrome were included. The quality of the included studies was assessed using the New Castle Ottawa Scale. Results: A total of 558 studies were identified in the initial search. After removing duplicates, 25 studies were screened based on title and abstract, of which 06 studies were included in this systematic review. Among them, 02 studies were of high quality and 04 studies were of moderate quality. After administration of genistein, a decrease in urinary GAG levels and HS levels was observed. Conclusion: Based on the limited evidence present in the literature, this systematic review suggests that genistein can be safely used to treat Sanfilippo syndrome as it lowers GAG levels. However, data on the long-term benefit profile of genistein and high-quality evidence are still needed as a conclusive result could not be withdrawn.

The need for neonatal jaundice screening awareness in the Pakistani population: short communication.

Neonatal jaundice is a common illness that affects around 80% of preterm and 50-60% of full-term newborn infants. It is one of the most common causes of neonatal death. Neonatal jaundice may be physiological or pathological. Physiologic jaundice is far more common than pathologic jaundice and accounts for most hyperbilirubinemia. Physiologic jaundice in neonates is due to greater hemoglobin breakdown compared to bilirubin clearance. While pathological jaundice occurs due to various infections, drug toxicity, inborn enzyme deficiencies, Rhesus fetal-maternal incompatibility, hypothyroidism, and congenital biliary duct obstruction diseases. In many parts of the world, midwives, and nurses perform spontaneous vaginal deliveries and they only rely on visual screening for neonatal jaundice. However, this is not reliable, especially for newborns having darker skin. Educating the mothers on screening for early detection of neonatal jaundice and seeking medical treatment in a country like Pakistan, which is considered a high-risk population, is crucial. Also, as most females give birth at home, hence, midwives' knowledge about neonatal jaundice also needs to be improved.

BONE MARROW OXALOSIS, A RARE CAUSE OF PANCYTOPENIA: A CASE REPORT

Primary hyperoxaluria is a rare congenital metabolic disease characterised by an overproduction of oxalate, secondary to a hepatic enzyme deficiency, alanine glyoxylate aminotransferase (AGT). Calcium oxalate crystals are deposited in many tissues. Involvement of the bone marrow is relatively rare. We report the case of a young 29-year-old patient with a history of recurrent renal lithiasis, progressing to end-stage chronic renal failure at the haemodialysis stage, admitted to the medical ward for investigation of mucocutaneous pallor and anaemia resistant to erythropoietin. Clinical and laboratory examination revealed an oedematous-ascitic syndrome and pancytopenia with normocytic normochromic anaemia. Imaging revealed moderate ascites and homogeneous splenomegaly. The myelogram was inconclusive. An osteomedullary biopsy was performed and showed deposits of oxalate crystals with bone marrow fibrosis associated with foreign body macrophagic granulomas. These crystals were grouped in a rosette and birefringent in polarised light. Primary hyperoxaluria is a rare disease. Involvement of the bone marrow indicates the advanced stage of the disease, hence the importance of anatomopathological diagnosis. Hepato-renal transplantation remains the only effective treatment for this disease.

Gene therapy for glycogen storage diseases.

Glycogen storage disorders (GSDs) are inherited disorders of metabolism resulting from the deficiency of individual enzymes involved in the synthesis, transport, and degradation of glycogen. This literature review summarizes the development of gene therapy for the GSDs. The abnormal accumulation of glycogen and deficiency of glucose production in GSDs lead to unique symptoms based upon the enzyme step and tissues involved, such as liver and kidney involvement associated with severe hypoglycemia during fasting and the risk of long-term complications including hepatic adenoma/carcinoma and end stage kidney disease in GSD Ia from glucose-6-phosphatase deficiency, and cardiac/skeletal/smooth muscle involvement associated with myopathy +/- cardiomyopathy and the risk for cardiorespiratory failure in Pompe disease. These symptoms are present to a variable degree in animal models for the GSDs, which have been utilized to evaluate new therapies including gene therapy and genome editing. Gene therapy for Pompe disease and GSD Ia has progressed to Phase I and Phase III clinical trials, respectively, and are evaluating the safety and bioactivity of adeno-associated virus vectors. Clinical research to understand the natural history and progression of the GSDs provides invaluable outcome measures that serve as endpoints to evaluate benefits in clinical trials. While promising, gene therapy and genome editing face challenges with regard to clinical implementation, including immune responses and toxicities that have been revealed during clinical trials of gene therapy that are underway. Gene therapy for the glycogen storage diseases is under development, addressing an unmet need for specific, stable therapy for these conditions.

Acute hepatic porphyrias: Recommendations for diagnosis and management with real-world examples

Acute hepatic porphyria (AHP) is a group of four rare inherited diseases, each resulting from a deficiency in a distinct enzyme in the heme biosynthetic pathway. Characterized by acute neurovisceral symptoms that may mimic other medical and psychiatric conditions, lack of recognition of the disease often leads to a delay in diagnosis and initiation of effective treatment. Biochemical testing for pathway intermediates that accumulate when the disease is active forms the basis for screening and establishing a diagnosis. Subsequent genetic analysis identifies the pathogenic variant, supporting screening of family members and genetic counseling. Management of AHP involves avoidance of known exogenous and hormonal triggers, symptomatic treatment, and prevention of recurrent attacks. Here we describe six case studies from our own real-world experience to highlight current recommendations and challenges associated with the diagnosis and long-term management of the disease.

Glycogen storage disease type I: Genetic etiology, clinical manifestations, and conventional and gene therapies.

Glycogen storage disease type I (GSDI) is an inherited metabolic disorder characterized by a deficiency of enzymes or proteins involved in glycogenolysis and gluconeogenesis, resulting in excessive intracellular glycogen accumulation. While GSDI is classified into four different subtypes based on molecular genetic variants, GSDIa accounts for approximately 80%. GSDIa and GSDIb are autosomal recessive disorders caused by deficiencies in glucose-6-phosphatase (G6Pase-α) and glucose-6-phosphate-transporter (G6PT), respectively. For the past 50 years, the care of patients with GSDI has been improved following elaborate dietary managements. GSDI patients currently receive dietary therapies that enable patients to improve hypoglycemia and alleviate early symptomatic signs of the disease. However, dietary therapies have many limitations with a risk of calcium, vitamin D, and iron deficiency and cannot prevent long-term complications, such as progressive liver and renal failure. With the deepening understanding of the pathogenesis of GSDI and the development of gene therapy technology, there is great progress in the treatment of GSDI. Here, we review the underlying molecular genetics and the current clinical management strategies of GSDI patients with an emphasis on promising experimental gene therapies.

Extensive mongoloid spots in mucopolysaccharidosis Type I Hurler syndrome

Lysosomal storage diseases are inherited metabolic disorders that are caused by enzyme deficiencies within the lysosomes. The most common lysosomal storage disorder associated with Mongolian spots (MSs) is GM1 gangliosidosis Type-1. We are reporting a case of Hurler disease with extensive MS. A 9-month-old girl, born to a consanguineously married couple, presented with a developmental delay with uneventful birth history. The presence of multiple mongoloid spots over the lumbosacral region and lateral abdominal wall was noticed since birth. Examination showed coarse facies with a depressed nasal bridge and a low-set ear. Multiple mongoloid macules were noted in the lumbosacral region. Serum enzyme assay level had decreased activity of alpha-L-iduronidase (IDUA). Exome sequencing revealed a homozygous mutation in exon 8 of the IDUA gene. Extensive MS can be seen in mucopolysaccharidosis (MPS) Type 1 in addition to commonly described GM1 gangliosidosis. The early diagnosis helps to start enzyme replacement therapy in MPS Type I, compared to currently no specific treatment available for GM1 gangliosidosis.

Citrulline in the management of patients with urea cycle disorders

BackgroundTreatment recommendations for urea cycle disorders (UCDs) include supplementation with amino acids involved in the urea cycle (arginine and/or citrulline, depending on the enzyme deficiency), to maximize ammonia excretion through the urea cycle, but limited data are available regarding the use of citrulline. This study retrospectively reviewed clinical and biological data from patients with UCDs treated with citrulline and/or arginine at a reference center since 1990. The aim was to describe the prescription, impact, and safety of these therapies. Data collection included patient background, treatment details, changes in biochemical parameters (plasma ammonia and amino acids concentrations), decompensations, and patient outcomes.ResultsOverall, 79 patients (median age at diagnosis, 0.9 months) received citrulline and/or arginine in combination with a restricted protein diet, most with ornithine transcarbamylase (n = 57, 73%) or carbamoyl phosphate synthetase 1 (n = 15, 19%) deficiencies. Most patients also received ammonium scavengers. Median follow-up was 9.5 years and median exposure to first treatment with arginine + citrulline, citrulline monotherapy, or arginine monotherapy was 5.5, 2.5, or 0.3 years, respectively. During follow-up, arginine or citrulline was administered at least once (as monotherapy or in combination) in the same proportion of patients (86.1%); the overall median duration of exposure was 5.9 years for arginine + citrulline, 3.1 years for citrulline monotherapy, and 0.6 years for arginine monotherapy. The most common switch was from monotherapy to combination therapy (41 of 75 switches, 54.7%). During treatment, mean ammonia concentrations were 35.9 µmol/L with citrulline, 49.8 µmol/L with arginine, and 53.0 µmol/L with arginine + citrulline. Mean plasma arginine concentrations increased significantly from the beginning to the end of citrulline treatment periods (from 67.6 µmol/L to 84.9 µmol/L, P < 0.05). At last evaluation, mean height and weight for age were normal and most patients showed normal or adapted behavior (98.7%) and normal social life (79.0%). Two patients (2.5%) experienced three treatment-related gastrointestinal adverse reactions.ConclusionsThis study underlines the importance of citrulline supplementation, either alone or together with arginine, in the management of patients with UCDs. When a monotherapy is considered, citrulline would be the preferred option in terms of increasing plasma arginine concentrations.

A glycomic workflow for LC–MS/MS analysis of urine glycosaminoglycan biomarkers in mucopolysaccharidoses

In recent years, several rational designed therapies have been developed for treatment of mucopolysaccharidoses (MPS), a group of inherited metabolic disorders in which glycosaminoglycans (GAGs) are accumulated in various tissues and organs. Thus, improved disease-specific biomarkers for diagnosis and monitoring treatment efficacy are of paramount importance. Specific non-reducing end GAG structures (GAG-NREs) have become promising biomarkers for MPS, as the compositions of the GAG-NREs depend on the nature of the lysosomal enzyme deficiency, thereby creating a specific pattern for each subgroup. However, there is yet no straightforward clinical laboratory platform which can assay all MPS-related GAG-NREs in one single analysis. Here, we developed and applied a GAG domain mapping approach for analyses of urine samples of ten MPS patients with various MPS diagnoses and corresponding aged-matched controls. We describe a nano-LC–MS/MS method of GAG-NRE profiling, utilizing 2-aminobenzamide reductive amination labeling to improve the sensitivity and the chromatographic resolution. Diagnostic urinary GAG-NREs were identified for MPS types IH/IS, II, IIIc, IVa and VI, corroborating GAG-NRE as biomarkers for these known enzyme deficiencies. Furthermore, a significant reduction of diagnostic urinary GAG-NREs in MPS IH (n = 2) and MPS VI (n = 1) patients under treatment was demonstrated. We argue that this straightforward glycomic workflow, designed for the clinical analysis of MPS-related GAG-NREs in one single analysis, will be of value for expanding the use of GAG-NREs as biomarkers for MPS diagnosis and treatment monitoring.

Mucopolysaccharidosis: An overview and new treatment modalities

Mucopolysaccharidosis is a lysosomal storage disorder, caused due to deficiency of enzymes required for the breakdown of Mucopolysaccharides. These undegraded Mucopolysaccharides accumulate in various tissues and cause characteristic features like neurological deficit, impaired motor function, developmental delay, hearing loss, behavioral problems, corneal clouding, glaucoma, respiratory distress, coarse facial features, skeletal deformities, and organomegaly. Based on deficient enzymes they have divided into subtypes Mucopolysaccharidosis I (MPS I) Hunter syndrome (I H / I HS / I S), Mucopolysaccharidosis II(MPS II) Hunter syndrome (severe and mild form), Mucopolysaccharidosis III (MPS III) Sanfilippo syndrome, Mucopolysaccharidosis IV(MPS IV) Morquio syndrome, Mucopolysaccharidosis VI(MPS VI) Maroteaux Lamy syndrome, Mucopolysaccharidosis VI (MPS VII) Sly syndrome. Diagnosis is classically based on clinical examination and urine analysis. Enzyme assay can also aid in diagnosis. Chorionic villi sampling and amniocentesis are also becoming popular. The main objective of treatment is to improve the quality of life. Symptomatic management includes daily exercise, physiotherapy, tonsillectomy, shunting surgery, and corneal transplantation. There are various recent concepts utilized for the treatment of Mucopolysaccharidosis. This review article emphasizes such treatment aspects as Hematopoietic stem cell therapy, Enzyme replacement therapy, Gene therapy, Nano-enabled therapy, and Substrate reduction therapy.

Natural history of GM1 gangliosidosis-Retrospective cohort study of 61 French patients from 1998 to 2019.

GM1 gangliosidosis is a rare lysosomal storage disorder associated with β-galactosidase enzyme deficiency. There are three types of GM1 gangliosidosis based on age of symptom onset, which correlate with disease severity. In 2019, we performed a retrospective multicentric study including all patients diagnosed with GM1 gangliosidosis in France since 1998. We had access to data for 61 of the 88 patients diagnosed between 1998 and 2019. There were 41 patients with type 1 (symptom onset ≤6 months), 11 with type 2a (symptom onset from 7 months to 2 years), 5 with type 2b (symptom onset from 2 to 3 years), and 4 with type 3 (symptom onset >3 years). The estimated incidence in France was 1/210,000. In patients with type 1, the first symptoms were hypotonia (26/41, 63%), dyspnea (7/41, 17%), and nystagmus (6/41, 15%), whereas in patients with type 2a these were psychomotor regression (9/11, 82%) and seizures (3/11, 27%). In types 2b and 3, the initial symptoms were mild, such as speech difficulties, school difficulties, and progressive psychomotor regression. Hypotonia was observed in all patients, except type 3. The mean overall survival was 23 months (95% confidence interval [CI]: 7, 39) for type 1 and 9.1 years (95% CI: 4.5, 13.5) for type 2a. To the best of our knowledge, this is one of the largest historical cohorts reported, which provides important information on the evolution of all types of GM1 gangliosidosis. These data could be used as a historical cohort in studies assessing potential therapies for this rare genetic disease. This article is protected by copyright. All rights reserved.

Glycogen storage diseases: An update.

Glycogen storage diseases (GSDs), also referred to as glycogenoses, are inherited metabolic disorders of glycogen metabolism caused by deficiency of enzymes or transporters involved in the synthesis or degradation of glycogen leading to aberrant storage and/or utilization. The overall estimated GSD incidence is 1 case per 20000-43000 live births. There are over 20 types of GSD including the subtypes. This heterogeneous group of rare diseases represents inborn errors of carbohydrate metabolism and are classified based on the deficient enzyme and affected tissues. GSDs primarily affect liver or muscle or both as glycogen is particularly abundant in these tissues. However, besides liver and skeletal muscle, depending on the affected enzyme and its expression in various tissues, multiorgan involvement including heart, kidney and/or brain may be seen. Although GSDs share similar clinical features to some extent, there is a wide spectrum of clinical phenotypes. Currently, the goal of treatment is to maintain glucose homeostasis by dietary management and the use of uncooked cornstarch. In addition to nutritional interventions, pharmacological treatment, physical and supportive therapies, enzyme replacement therapy (ERT) and organ transplantation are other treatment approaches for both disease manifestations and long-term complications. The lack of a specific therapy for GSDs has prompted efforts to develop new treatment strategies like gene therapy. Since early diagnosis and aggressive treatment are related to better prognosis, physicians should be aware of these conditions and include GSDs in the differential diagnosis of patients with relevant manifestations including fasting hypoglycemia, hepatomegaly, hypertransaminasemia, hyperlipidemia, exercise intolerance, muscle cramps/pain, rhabdomyolysis, and muscle weakness. Here, we aim to provide a comprehensive review of GSDs. This review provides general characteristics of all types of GSDs with a focus on those with liver involvement.