Isolated short stature as the only presenting symptom of glycogen storage disease type 0a in a Chinese child: A case report.

RATIONALE: Glycogen storage disease type 0a (GSD0a) is a rare autosomal recessive disorder caused by glycogen synthase deficiency. Short stature is a characteristic feature in 29% of GSD0a patients, but isolated short stature as the only presenting symptom is exceedingly rare, with only 2 cases reported worldwide. PATIENT CONCERNS: A 4-year-old girl presented with persistent growth retardation despite previous treatment for renal tubular acidosis. DIAGNOSES: Based on clinical presentation and whole exome sequencing results, the patient was diagnosed with GSD0a. INTERVENTIONS: Uncooked cornstarch therapy was initiated at 2 g/kg every 6 hours. OUTCOMES: After 3 years of treatment, the patient's height SDS improved from -2.24 to -1.06, with enhanced glycemic control and no complications. LESSONS: This case emphasizes considering GSD0a in unexplained short stature and the value of continuous glucose monitoring. Early diagnosis and treatment can optimize growth in GSD0a patients.

Short and long-term acceptability and efficacy of extended-release cornstarch in the hepatic glycogen storage diseases: results from the Glyde study.

BACKGROUND: Hypoglycaemia is the primary manifestation of all the hepatic types of glycogen storage disease (GSD). In 2008, Glycosade®, an extended-release waxy maize cornstarch, was reported as an alternative to uncooked cornstarch (UCCS) which could prolong the duration of fasting in the GSD population. To date, there has been minimal published experience in (a) young children, (b) the ketotic forms of GSD, and (c) with daytime dosing. The Glyde study was created as a prospective, global initiative to test the efficacy and tolerance of Glycosade use across a broader and more diverse population. METHODS: A randomised double-blind cross-over fasting study assessing the tolerance and efficacy of Glycosade compared with cornstarch was performed across disease types and ages. Participants and clinicians chose the product deemed superior, whilst still blinded. Participants were followed for 2 years to assess long-term metabolic control, growth, and quality of life. RESULTS: Sixty-one participants (age 2-62 years; 59% female) were enrolled, and 58 participants completed the fasting studies (28 GSD I; 30 GSD III, VI, IX). Glycosade improved duration of fasting in GSD I and duration of fasting without ketosis in the ketotic forms. Chronic Glycosade use was chosen by 69% of participants. Those treated with Glycosade for the 2-year chronic phase used fewer doses of therapy while markers of metabolic control remained stable. CONCLUSION: The Glyde study is the first multi-centre international trial demonstrating the efficacy and tolerance of Glycosade in a large cohort of hepatic GSD patients across a diverse international population. The ability to use fewer doses of therapy per day and avoidance of overnight therapy may improve compliance, safety, and quality of life without sacrificing metabolic control.

Induced Pluripotent Stem Cells and CRISPR-Cas9 Innovations for Treating Alpha-1 Antitrypsin Deficiency and Glycogen Storage Diseases.

Human induced pluripotent stem cell (iPSC) and CRISPR-Cas9 gene-editing technologies have become powerful tools in disease modeling and treatment. By harnessing recent biotechnological advancements, this review aims to equip researchers and clinicians with a comprehensive and updated understanding of the evolving treatment landscape for metabolic and genetic disorders, highlighting how iPSCs provide a unique platform for detailed pathological modeling and pharmacological testing, driving forward precision medicine and drug discovery. Concurrently, CRISPR-Cas9 offers unprecedented precision in gene correction, presenting potential curative therapies that move beyond symptomatic treatment. Therefore, this review examines the transformative role of iPSC technology and CRISPR-Cas9 gene editing in addressing metabolic and genetic disorders such as alpha-1 antitrypsin deficiency (A1AD) and glycogen storage disease (GSD), which significantly impact liver and pulmonary health and pose substantial challenges in clinical management. In addition, this review discusses significant achievements alongside persistent challenges such as technical limitations, ethical concerns, and regulatory hurdles. Future directions, including innovations in gene-editing accuracy and therapeutic delivery systems, are emphasized for next-generation therapies that leverage the full potential of iPSC and CRISPR-Cas9 technologies.

Proteomic profiling of polyglucosan bodies associated with glycogenin-1 deficiency in skeletal muscle.

AIMS: Polyglucosan storage disorders represent an emerging field within neurodegenerative and neuromuscular conditions, including Lafora disease (EPM2A, EPM2B), adult polyglucosan body disease (APBD, GBE1), polyglucosan body myopathies associated with RBCK1 deficiency (PGBM1, RBCK1) or glycogenin-1 deficiency (PGBM2, GYG1). While the storage material primarily comprises glycans, this study aimed to gain deeper insights into the protein components by proteomic profiling of the storage material in glycogenin-1 deficiency. METHODS: We employed molecular genetic analyses, quantitative mass spectrometry of laser micro-dissected polyglucosan bodies and muscle homogenate, immunohistochemistry and western blot analyses in muscle tissue from a 45-year-old patient with proximal muscle weakness from late teenage years due to polyglucosan storage myopathy. RESULTS: The muscle tissue exhibited a complete absence of glycogenin-1 due to a novel homozygous deep intronic variant in GYG1 (c.7+992T>G), introducing a pseudo-exon causing frameshift and a premature stop codon. Accumulated proteins in the polyglucosan bodies constituted components of glycogen metabolism, protein quality control pathways and desmin. Muscle fibres containing polyglucosan bodies frequently exhibited depletion of normal glycogen. CONCLUSIONS: The absence of glycogenin-1, a protein important for glycogen synthesis initiation, causes storage of polyglucosan that displays accumulation of several proteins, including those essential for glycogen synthesis, sequestosome 1/p62 and desmin, mirroring findings in RBCK1 deficiency. These results suggest shared pathogenic pathways across different diseases exhibiting polyglucosan storage. Such insights have implications for therapy in these rare yet devastating and presently untreatable disorders.

Genotypic and phenotypic features of 39 Chinese patients with glycogen storage diseases type I, VI, and IX.

Glycogen storage diseases (GSDs) are abnormally inherited glycogen metabolism mainly affecting the liver, muscles, and heart. Deficiency of proteins involved in glycogen metabolism caused by genetic mutations are responsible for different subtype of GSDs. However, there are still some challenges in diagnosing GSD. This study includes 39 suspected GSDs patients from unrelated families in China. Next-generation sequencing (NGS) was used to investigate the reason for their diseases at the genetic level. Finally, all 39 patients were diagnosed with GSDs, including 20 GSD-Ia, 4 GSD-VI, and 15 GSD IX (12 GSD-IXa patients and 3 GSD-IXb patients). Thirty-two mutations in G6PC1, PYGL, PHKA2, and PHKB genes were identified, with 14 of them being novel variants. The pathogenicity of novel variants was classified according to ACMG guildlines and predicted by in slico algorithms. Mutations p.L216L and p.R83H in G6PC1 gene may be the hot spot mutation in Chinese. Hearing impairment is a rare clinical feature of GSD Ia, which has also been observed in our cohort. The severity of GSD VI and IX was indicated by our patients. Close follow-up should be applied to GSD VI and IX patients. Our findings provided evidence for building the phenotype-genotype of GSDs and expanded the mutation spectrum of related genes.

A rare co-occurrence of phosphorylase kinase deficiency (GSD type IXd) and alpha-glycosidase deficiency (GSD Type II) in a 53-year-old man presenting with an atypical glycogen storage disease phenotype.

Glycogen Storage Disease (GSD) IXd, caused by PHKA1 gene mutations, is an X-linked rare disorder that can be asymptomatic or associated with exercise intolerance. GSD type II is an autosomal recessive disorder caused by mutations in the GAA gene that lead to severe cardiac and skeletal muscle myopathy. We report the first case of co-occurrence of type IXd and type II GSDs in a 53-year-old man with an atypical glycogen storage disease presentation consisting in myalgia in the lower limbs at both rest and after exercise and increased levels of transaminases from the age of 16. At the age of 43, the patient presented a steppage gait, inability to run and walk on his heels, hypotrophy of the pectoral and proximal muscles, reflexes not elicitable, and CK levels 3.6 times the upper reference limit. Next Generation Sequencing (NGS) identified one variant in the PHKA1 gene, c.1360A > G p.Ile454Val (exon 14) inherited by his mother, and two heterozygous variants in the GAA gene, c.784G > A (exon 4) and c.956-6T > C (exon 6). A review of GSD IXd cases reported to date in the literature is also provided.

Endocrine involvement in hepatic glycogen storage diseases: pathophysiology and implications for care.

Hepatic glycogen storage diseases constitute a group of disorders due to defects in the enzymes and transporters involved in glycogen breakdown and synthesis in the liver. Although hypoglycemia and hepatomegaly are the primary manifestations of (most of) hepatic GSDs, involvement of the endocrine system has been reported at multiple levels in individuals with hepatic GSDs. While some endocrine abnormalities (e.g., hypothalamic­pituitary axis dysfunction in GSD I) can be direct consequence of the genetic defect itself, others (e.g., osteopenia in GSD Ib, insulin-resistance in GSD I and GSD III) may be triggered by the (dietary/medical) treatment. Being aware of the endocrine abnormalities occurring in hepatic GSDs is essential (1) to provide optimized medical care to this group of individuals and (2) to drive research aiming at understanding the disease pathophysiology. In this review, a thorough description of the endocrine manifestations in individuals with hepatic GSDs is presented, including pathophysiological and clinical implications.

Myofiber-type-dependent 'boulder' or 'multitudinous pebble' formations across distinct amylopectinoses.

At least five enzymes including three E3 ubiquitin ligases are dedicated to glycogen's spherical structure. Absence of any reverts glycogen to a structure resembling amylopectin of the plant kingdom. This amylopectinosis (polyglucosan body formation) causes fatal neurological diseases including adult polyglucosan body disease (APBD) due to glycogen branching enzyme deficiency, Lafora disease (LD) due to deficiencies of the laforin glycogen phosphatase or the malin E3 ubiquitin ligase and type 1 polyglucosan body myopathy (PGBM1) due to RBCK1 E3 ubiquitin ligase deficiency. Little is known about these enzymes' functions in glycogen structuring. Toward understanding these functions, we undertake a comparative murine study of the amylopectinoses of APBD, LD and PGBM1. We discover that in skeletal muscle, polyglucosan bodies form as two main types, small and multitudinous ('pebbles') or giant and single ('boulders'), and that this is primarily determined by the myofiber types in which they form, 'pebbles' in glycolytic and 'boulders' in oxidative fibers. This pattern recapitulates what is known in the brain in LD, innumerable dust-like in astrocytes and single giant sized in neurons. We also show that oxidative myofibers are relatively protected against amylopectinosis, in part through highly increased glycogen branching enzyme expression. We present evidence of polyglucosan body size-dependent cell necrosis. We show that sex influences amylopectinosis in genotype, brain region and myofiber-type-specific fashion. RBCK1 is a component of the linear ubiquitin chain assembly complex (LUBAC), the only known cellular machinery for head-to-tail linear ubiquitination critical to numerous cellular pathways. We show that the amylopectinosis of RBCK1 deficiency is not due to loss of linear ubiquitination, and that another function of RBCK1 or LUBAC must exist and operate in the shaping of glycogen. This work opens multiple new avenues toward understanding the structural determinants of the mammalian carbohydrate reservoir critical to neurologic and neuromuscular function and disease.

Report of an Iranian child with chronic abdominal pain and constipation diagnosed as glycogen storage disease type IX: a case report.

BACKGROUND: Glycogen storage disease type IX is a rare disorder that can cause a wide variety of symptoms depending on the specific deficiency of the phosphorylase kinase enzyme and the organs it affects. CASE PRESENTATION: A 4-and-a-half-year-old Caucasian girl was referred to our clinic with a liver biopsy report indicating a diagnosis of glycogen storage disease. Prior to being referred to our clinic, the patient had been under the care of pediatric gastroenterologists. The patient's initial symptoms included chronic abdominal pain, constipation, and elevated liver transaminase. With the help of the pediatric gastroenterologists, cholestasis, Wilson disease, and autoimmune hepatitis were ruled out. Given that glycogen storage diseases type I and type III are the most common, we initially managed the patient with frequent feedings and a diet that included complex carbohydrates such as a corn starch supplement and a lactose restriction. Following an unfavorable growth velocity and hepatomegaly during the follow-up period, genetic analysis was conducted, which revealed a novel mutation of the phosphorylase kinase regulatory subunit beta gene- a c.C412T (P.Q138x) mutation. As the diagnosis of glycogen storage disease type IX was confirmed, the treatment regimen was altered to a high protein diet (more than 2 g/kg/day) and a low fat diet. CONCLUSION: Given the mild and varied clinical manifestations of glycogen storage disease type IX, it is possible for the diagnosis to be overlooked. It is important to consider glycogen storage disease type IX in children who present with unexplained hepatomegaly and elevated transaminase levels. Furthermore, due to the distinct management of glycogen storage disease type IX compared with glycogen storage disease type I and glycogen storage disease type III, genetic analysis is essential for an accurate diagnosis.

Severe neuromuscular forms of glycogen storage disease type IV: Histological, clinical, biochemical, and molecular findings in a large French case series.

Glycogen storage disease type IV (GSD IV), also called Andersen disease, or amylopectinosis, is a highly heterogeneous autosomal recessive disorder caused by a glycogen branching enzyme (GBE, 1,4-alpha-glucan branching enzyme) deficiency secondary to pathogenic variants on GBE1 gene. The incidence is evaluated to 1:600 000 to 1:800 000 of live births. GBE deficiency leads to an excessive deposition of structurally abnormal, amylopectin-like glycogen in affected tissues (liver, skeletal muscle, heart, nervous system, etc.). Diagnosis is often guided by histological findings and confirmed by GBE activity deficiency and molecular studies. Severe neuromuscular forms of GSD IV are very rare and of disastrous prognosis. Identification and characterization of these forms are important for genetic counseling for further pregnancies. Here we describe clinical, histological, enzymatic, and molecular findings of 10 cases from 8 families, the largest case series reported so far, of severe neuromuscular forms of GSD IV along with a literature review. Main antenatal features are: fetal akinesia deformation sequence or arthrogryposis/joint contractures often associated with muscle atrophy, decreased fetal movement, cystic hygroma, and/or hydrops fetalis. If pregnancy is carried to term, the main clinical features observed at birth are severe hypotonia and/or muscle atrophy, with the need for mechanical ventilation, cardiomyopathy, retrognathism, and arthrogryposis. All our patients were stillborn or died within 1 month of life. In addition, we identified five novel GBE1 variants.

Savory Cracker Development for Blood Glucose Control and Management: Glycogen Storage Diseases.

The blood glucose response of savory slow energy-release crackers (GLY-HYP) were evaluated in volunteers carrying glycogen storage diseases (GSDs), Types I (Ia) and IV. The crackers have been shown previously to provide a "flat" slow glucose response in healthy volunteers, for up to 4 h. On average for the mixed-sex volunteer group aged 53 to 70 for Type I, the blood glucose concentration increased from baseline to a maximum of 9.5 mmol/L at 60 min and remained above baseline for up to 210 min; overall, above 5 mmol/L for 4 h. In common with healthy individuals, a relatively flat blood glucose response was recorded. For Type IV, mixed-sex patients aged between 55 and 72, the blood glucose concentration reached maximum of 10.2 mmol/L at 45 min and then stayed above baseline for 150 min. Again, overall, above 5 mmol/L for 4 h. Altogether, these data indicate that these crackers would provide a valuable contribution to the nutritional needs of people of different age groups with GSDs (Clinical Registration Number: HRC10032021).

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.

Three novel SLC37A4 variants in glycogen storage disease type 1b and a literature review.

Glycogen storage disease type 1b (GSD1b) is a rare genetic disorder, resulting from mutations in the SLC37A4 gene located on chromosome 11q23.3. Although the SLC37A4 gene has been identified as the pathogenic gene for GSD1b, the complete variant spectrum of this gene remains to be fully elucidated. In this study, we present three patients diagnosed with GSD1b through genetic testing. We detected five variants of the SLC37A4 gene in these three patients, with three of these mutations (p. L382Pfs*15, p. G117fs*28, and p. T312Sfs*13) being novel variants not previously reported in the literature. We also present a literature review and general overview of the currently reported SLC37A4 gene variants. Our study expands the mutation spectrum of SLC37A4, which may help enable genetic testing to facilitate prompt diagnosis, appropriate intervention, and genetic counseling for affected families.

Glycogen Storage Disease: Expert Opinion on Clinical Diagnosis Revisited after Molecular Testing.

This study sought to analyze whether an accurate diagnosis of the type and subtype of hepatic Glycogen Storage Diseases (GSDs) could be performed based on general clinical and biochemical aspects via comparing the proposed diagnostic hypotheses with the molecular results. Twelve physicians with experience in hepatic GSDs reviewed 45 real cases comprising a standardized summary of clinical and laboratory data. There was no relation between the hit rate and the time since graduation, the time of experience in GSD, and the number of patients treated during their careers. The average assertiveness was 47%, with GSD Ia and Ib being the best-identified types, while no expert correctly identified GSD IXc. Underage investigation for later manifestations, incomplete clinical description, and complementary analysis, the overvaluation of a specific clinical finding ("false positive") or the discarding of the diagnosis in the absence of it ("false negative"), as well as the lack of knowledge of the rarest GSD types, may have impacted the accuracy of the assessment. This study emphasized that characteristics considered as determinants in identifying the specific types or subtypes of GSD are not exclusive, thus becoming factors that may have induced the evaluators to misdiagnose.

Case 318: Adult Polyglucosan Body Disease.

HISTORY: A 72-year-old man sought care for a cognitive deterioration over the past 5 years. There was a documented decline in his performance on the Mini-Mental State Examination (30 of 30 in 2016, 23 of 30 in 2021), with mainly episodic memory impairment. A more detailed history revealed a gait problem, paresthesia in both feet, and nocturnal urinary frequency. Clinical examination findings were suggestive of a length-dependent polyneuropathy. In addition, a right-sided Babinski sign was noted. Electromyography and a nerve conduction study corroborated a peripheral axonal sensorimotor neuropathy. MRI of the brain was performed.