Role of continuous glucose monitoring in the management of glycogen storage disorders

Impact of Flash Glucose Monitoring in Adults with Inherited Metabolic Disorders at Risk of Hypoglycemia

BACKGROUND

This study addresses hypoglycemia in adults with inherited metabolic disorders (IMDs), highlighting the importance of intermittently scanned continuous glucose monitoring (isCGM). Despite the elevated risk of hypoglycemia in an important group of these diseases, the use of isCGM remains uncommon and there is limited evidence supporting its effectiveness.

METHODS

A longitudinal quasi-experimental study was performed in 18 adults with IMDs, evaluating the use of isCGM for 2 months. Time in hypoglycemia (TBR), hyperglycemia (TAR), and time in range (TIR) were monitored, in addition to symptomatic and asymptomatic hypoglycemic events. Follow-up visits were performed at 7 days, 14 days, and 2 months.

RESULTS

TBR < 70 mg/dL was significantly reduced from 1.5% at baseline to 0% at 2 months. A decrease in the number and duration of hypoglycemic events was also observed. In some IMD subgroups, isCGM enabled detection of asymptomatic hypoglycemia and adjustment to dietary management, improving glycemic control.

CONCLUSIONS

isCGM is effective in detecting and reducing hypoglycemia in adults with IMDs, optimizing nutritional therapy, and improving the quality of life of patients and their families.

Personalized management of hepatic glycogen storage disorders: The role of continuous glucose monitoring

OBJECTIVE

Glycogen storage disorders (GSD), inherent disorders of carbohydrate metabolism, feature hypoglycemia as a hallmark. Normoglycemia and glucose monitoring are pivotal in disease management. Conventional glucometer-based monitoring may overlook hypoglycemic trends. This study assesses glycemic control in Asian Indian GSD children using continuous glucose monitoring (CGM) and its role in facilitating dietary adjustments.

METHODS

A pre-post study enrolled molecularly confirmed GSDI, GSDIII, GSDVI, and GSDIX patients for baseline dietary compliance and CGM-based glycemic status evaluation. Hypoglycemic patients were stratified into diet-compliant and diet-noncompliant groups. Noncompliant patients received dietary reinforcement; compliant individuals underwent dietary adjustments. Repeat CGM (rCGM) was performed 6 weeks to 6 months postadjustments. Clinical and metabolic parameters were re-evaluated at 6 months.

RESULTS

Of the 20 patients assessed at baseline, 11 were diet compliant. Six among these exhibited hypoglycemia, prompting diet adjustments. Among nine noncompliant patients, eight experienced hypoglycemia and received diet reinforcement. rCGM in 10 patients (five GSDI, three GSDIII, and two GSDIXc) showed a significant reduction in hypoglycemia duration in all. An improvement in height and body mass index was observed in all GSDI and GSDIII patients. Triglyceride levels, raised at baseline in two GSDI and one GSDIII, showed a substantial decline in one GSDI patient. Hepatic transaminase levels decreased in both GSDIXc patients. Plasma lactate levels decreased in all GSDI patients.

CONCLUSION

CGM is an efficacious adjunct in the personalized management of hepatic GSD patients, in the Asian Indian population. The study also underscores the need for long-term follow-up to determine the role of glycemic management in growth, general well-being, and metabolic control in the GSD subtypes.

Continuous glucose monitoring (CGM) for effective glucose control in a pregnant woman living with type IIIa glycogenosis. A case report

BACKGROUND & AIMS

Glycogenosis type III is a rare autosomal recessive disease caused by a mutation in the AGL gene that results in a deficiency of the glycogen debranching enzyme. This deficiency impairs fasting tolerance and leads to hypoglycemia. While the symptomatology tends to improve with age, pregnancy can trigger a recurrence of hypoglycemia due to increased carbohydrate requirements. Since the late 1990s, continuous glucose monitoring (CGM) has been used in insulin-dependent diabetes to aid in the prevention of hypoglycemia. It has also been employed in type I glycogenosis for the same purpose. However, it has never been evaluated for the prevention of hypoglycemia in pregnant women with type III glycogenosis.

CASE

report: We present the case of a 32-year-old pregnant woman with type IIIa glycogenosis diagnosed at the age of 2 years old. The resurgence of nocturnal hypoglycemia initially led to the reinstatement of continuous nocturnal nutrition. We established remote glucose monitoring via CGM, facilitating medical and dietary teleconsultations until delivery. These teleconsultations enabled dietary adjustment according to the patient's needs, based on the CGM data. This subsequently led to a reduction in the frequency and duration of nocturnal hypoglycemia, even after discontinuing continuous nutrition. No severe hypoglycemia was observed.

DISCUSSION

Our results suggest that CGM combined with telemonitoring can provide effective support for individuals living with glycogenosis during pregnancy and may eliminate the need for resuming continuous nocturnal enteral nutrition. However, these results need to be confirmed with additional patient cases.

CONCLUSION

CGM is a safe tool to limit the risk of hypoglycemia and to improve the quality of life of pregnant patients with type III glycogenosis.

Continuous glucose monitoring in patients with inherited metabolic disorders at risk for Hypoglycemia and Nutritional implications

Managing Inherited Metabolic Disorders (IMDs) at risk for hypoglycemia, such as Glycogen Storage Diseases (GSDs), Hereditary Fructose Metabolism Disorders (HFMDs) and Congenital Hyperinsulinism (CH), poses challenges in dietary treatments and blood glucose monitoring. The effectiveness of Continuous Glucose Monitoring (CGM) remains a subject of ongoing debate, with IMD guidelines maintaining caution. Therefore, a systematic evaluation is needed to understand the potential benefits of CGM during dietary interventions. A systematic literature review was conducted in PubMed according to the PICOS model and PRISMA recommendations on studies published from January 01, 2003, up to October 15, 2023 (PROSPERO CRD42024497744). The risk of bias was assessed using NIH Quality Assessment Tools. Twenty-four studies in GSDs (n = 13), CH (n = 10), and HFMDs (n = 1) were analyzed. In GSDs, Real-time CGM (Rt-CGM) was associated with metabolic benefits during nutritional interventions, proving to be an accurate system for hypoglycemia detection although with some concerns about reliability. Rt-CGM in CH, primarily involving children, also showed potential benefits for glycemic control and metabolic stability with acceptable accuracy, although its use during dietary changes was limited. Few experiences on Flash Glucose Monitoring (FGM) were reported, with some concerns about reliability. Overall, the studies analyzed presented different designs, and their quality was predominantly fair or poor. Heterogeneity and limited consensus on reliability and glycemic targets underscore the need for prospective studies and future recommendations for the use of CGM in optimizing nutritional status and providing personalized dietary education in individuals with IMDs prone to hypoglycemia.

Nutrition Management in Children Less than 5 Years of Age with Glycogen Storage Disease Type I: Survey Results

Background: Nutrition management for GSD Type I (GSDI; OMIM #232200, 232220) is complex, with the goal being to maintain euglycemia while minimizing metabolic derangements. Management guidelines were published in 2002 and 2014. However, there is limited information on the nuances of nutrition management and the unique feeding challenges of children. Methods: A REDCap survey focusing on staffing and current practices in the nutrition management of children with GSD I who were <5 years of age was sent to the metabolic dietitian's listserv and GMDI membership in 8/2023. Results: There were 21 North American respondents. In 17/21 clinics (81%), Prosobee® was the primary choice for infant formula. Dietitians used different methods to determine hourly glucose needs. Fasting recommendations ranged from 1 to 3 h, and the use of nighttime continuous feeding was common. Cornstarch was started between 6 and 12 months of age. Most clinics did not use Glycosade® for children <5 years of age. Oral motor dysfunction, gagging, and lack of interest in food were common. Continuous glucose monitoring (CGM) devices were recommended in 20 clinics (95%). Most clinics followed patients on an outpatient basis. All clinics provided a hypoglycemia management plan; however, there was wide variability in practice. Conclusion: This survey highlights the variability in the care of individuals <5 years of age with GSD I. Updated guidelines are needed to help address the unique nutrition challenges in this age group.

Continuous glucose monitoring metrics in people with liver glycogen storage disease and idiopathic ketotic hypoglycemia: A single-center, retrospective, observational study

BACKGROUND

Cohort data on continuous glucose monitoring (CGM) metrics are scarce for liver glycogen storage diseases (GSDs) and idiopathic ketotic hypoglycemia (IKH). The aim of this study was to retrospectively describe CGM metrics for people with liver GSDs and IKH.

PATIENTS AND METHODS

CGM metrics (descriptive, glycemic variation and glycemic control parameters) were calculated for 47 liver GSD and 14 IKH patients, categorized in cohorts by disease subtype, age and treatment status, and compared to published age-matched CGM metrics from healthy individuals. Glycemic control was assessed as time-in-range (TIR; ≥3.9 - ≤7.8 and ≥3.9 - ≤10.0 mmol/L), time-below-range (TBR; <3.0 mmol/L and ≥3.0 - ≤3.9 mmol/L), and time-above-range (TAR; >7.8 and >10.0 mmol/L).

RESULTS

Despite all patients receiving dietary treatment, GSD cohorts displayed significantly different CGM metrics compared to healthy individuals. Decreased TIR together with increased TAR were noted in GSD I, GSD III, and GSD XI (Fanconi-Bickel syndrome) cohorts (all p < 0.05). In addition, all GSD I cohorts showed increased TBR (all p < 0.05). In GSD IV an increased TBR (p < 0.05) and decreased TAR were noted (p < 0.05). In GSD IX only increased TAR was observed (p < 0.05). IKH patient cohorts, both with and without treatment, presented CGM metrics similar to healthy individuals.

CONCLUSION

Despite dietary treatment, most liver GSD cohorts do not achieve CGM metrics comparable to healthy individuals. International recommendations on the use of CGM and clinical targets for CGM metrics in liver GSD patients are warranted, both for patient care and clinical trials.

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., hypothalamic‑pituitary 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.

3D Printing of Dietary Products for the Management of Inborn Errors of Intermediary Metabolism in Pediatric Populations

The incidence of Inborn Error of Intermediary Metabolism (IEiM) diseases may be low, yet collectively, they impact approximately 6-10% of the global population, primarily affecting children. Precise treatment doses and strict adherence to prescribed diet and pharmacological treatment regimens are imperative to avert metabolic disturbances in patients. However, the existing dietary and pharmacological products suffer from poor palatability, posing challenges to patient adherence. Furthermore, frequent dose adjustments contingent on age and drug blood levels further complicate treatment. Semi-solid extrusion (SSE) 3D printing technology is currently under assessment as a pioneering method for crafting customized chewable dosage forms, surmounting the primary limitations prevalent in present therapies. This method offers a spectrum of advantages, including the flexibility to tailor patient-specific doses, excipients, and organoleptic properties. These elements are pivotal in ensuring the treatment's efficacy, safety, and adherence. This comprehensive review presents the current landscape of available dietary products, diagnostic methods, therapeutic monitoring, and the latest advancements in SSE technology. It highlights the rationale underpinning their adoption while addressing regulatory aspects imperative for their seamless integration into clinical practice.

Glycogen storage diseases

Glycogen storage diseases (GSDs) are a group of rare, monogenic disorders that share a defect in the synthesis or breakdown of glycogen. This Primer describes the multi-organ clinical features of hepatic GSDs and muscle GSDs, in addition to their epidemiology, biochemistry and mechanisms of disease, diagnosis, management, quality of life and future research directions. Some GSDs have available guidelines for diagnosis and management. Diagnostic considerations include phenotypic characterization, biomarkers, imaging, genetic testing, enzyme activity analysis and histology. Management includes surveillance for development of characteristic disease sequelae, avoidance of fasting in several hepatic GSDs, medically prescribed diets, appropriate exercise regimens and emergency letters. Specific therapeutic interventions are available for some diseases, such as enzyme replacement therapy to correct enzyme deficiency in Pompe disease and SGLT2 inhibitors for neutropenia and neutrophil dysfunction in GSD Ib. Progress in diagnosis, management and definitive therapies affects the natural course and hence morbidity and mortality. The natural history of GSDs is still being described. The quality of life of patients with these conditions varies, and standard sets of patient-centred outcomes have not yet been developed. The landscape of novel therapeutics and GSD clinical trials is vast, and emerging research is discussed herein.

French recommendations for the management of glycogen storage disease type III

The aim of the Protocole National De Diagnostic et de Soins/French National Protocol for Diagnosis and Healthcare (PNDS) is to provide advice for health professionals on the optimum care provision and pathway for patients with glycogen storage disease type III (GSD III).The protocol aims at providing tools that make the diagnosis, defining the severity and different damages of the disease by detailing tests and explorations required for monitoring and diagnosis, better understanding the different aspects of the treatment, defining the modalities and organisation of the monitoring. This is a practical tool, to which health care professionals can refer. PNDS cannot, however, predict all specific cases, comorbidities, therapeutic particularities or hospital care protocols, and does not seek to serve as a substitute for the individual responsibility of the physician in front of his/her patient.

Continuous glucose monitoring for children with hypoglycaemia: Evidence in 2023

In 2023, childhood hypoglycaemia remains a major public health problem and significant risk factor for consequent adverse neurodevelopment. Irrespective of the underlying cause, key elements of clinical management include the detection, prediction and prevention of episodes of hypoglycaemia. These tasks are increasingly served by Continuous Glucose Monitoring (CGM) devices that measure subcutaneous glucose at near-continuous frequency. While the use of CGM in type 1 diabetes is well established, the evidence for widespread use in rare hypoglycaemia disorders is less than convincing. However, in the few years since our last review there have been multiple developments and increased user feedback, requiring a review of clinical application. Despite advances in device technology, point accuracy of CGM remains low for children with non-diabetes hypoglycaemia. Simple provision of CGM devices has not replicated the efficacy seen in those with diabetes and is yet to show benefit. Machine learning techniques for hypoglycaemia prevention have so far failed to demonstrate sufficient prediction accuracy for real world use even in those with diabetes. Furthermore, access to CGM globally is restricted by costs kept high by the commercially-driven speed of technical innovation. Nonetheless, the ability of CGM to digitally phenotype disease groups has led to a better understanding of natural history of disease, facilitated diagnoses and informed changes in clinical management. Large CGM datasets have prompted re-evaluation of hypoglycaemia incidence and facilitated improved trial design. Importantly, an individualised approach and focus on the behavioural determinants of hypoglycaemia has led to real world reduction in hypoglycaemia. In this state of the art review, we critically analyse the updated evidence for use of CGM in non-diabetic childhood hypoglycaemia disorders since 2020 and provide suggestions for qualified use.

A Prospective Study on Continuous Glucose Monitoring in Glycogen Storage Disease Type Ia: Toward Glycemic Targets

CONTEXT

Although previous research has shown the benefit of continuous glucose monitoring (CGM) for hepatic glycogen storage diseases (GSDs), current lack of prospectively collected CGM metrics and glycemic targets for CGM-derived outcomes in the hepatic GSD population limits its use.

OBJECTIVE

To assess CGM metrics for glycemic variation and glycemic control in adult patients with GSDIa as compared to matched healthy volunteers.

DESIGN

Prospective CGM data were collected during the ENGLUPRO GSDIa trial (NCT04311307) in which a Dexcom G6 device was used. Ten adult patients with GSDIa and 10 age-, sex- and body mass index-matched healthy volunteers were enrolled. Capillary blood glucose was concurrently measured during 2 standardized 2-hour time intervals. Descriptive [eg, glycemic variability (GV), time below range, time in range (TIR), time above range (TAR)] and advanced (ie, first- and second-order derivatives, Fourier analysis) CGM outcomes were calculated. For each descriptive CGM outcome measure, 95% CIs were computed in patients with GSDIa and healthy volunteers, respectively.

RESULTS

CGM overestimation was higher under preprandial and level 1 hypoglycemia (ie, capillary glucose values ≥ 3.0 mmol/L and < 3.9 mmol/L) conditions. GV and TAR were higher while TIR was lower in patients with GSDIa compared to healthy volunteers (P < 0.05). Three patients with GSDIa showed descriptive CGM outcomes outside the calculated 95% CI in GSDIa patients. Advanced CGM analysis revealed a distinct pattern (ie, first- and second-order derivatives and glucose curve amplitude) in each of these 3 patients within the patients group.

CONCLUSIONS

This is the first study to prospectively compare CGM outcomes between adult patients with GSDIa and matched healthy volunteers. The generation of a set of CGM metrics will provide guidance in using and interpreting CGM data in GSDIa and will be useful for the definition of glycemic targets for CGM in patients with GSDIa. Future studies should investigate the prognostic value of CGM outcomes and their major determinants in patients with GSDIa.

Dynamic Methods for Childhood Hypoglycemia Phenotyping: A Narrative Review

Hypoglycemia results from an imbalance between glucose entering the blood compartment and glucose demand, caused by a defect in the mechanisms regulating postprandial glucose homeostasis. Hypoglycemia represents one of the most common metabolic emergencies in childhood, potentially leading to serious neurologic sequelae, including death. Therefore, appropriate investigation of its specific etiology is paramount to provide adequate diagnosis, specific therapy and prevent its recurrence. In the absence of critical samples for biochemical studies, etiological assessment of children with hypoglycemia may include dynamic methods, such as in vivo functional tests, and continuous glucose monitoring. By providing detailed information on actual glucose fluxes in vivo, proof-of-concept studies have illustrated the potential (clinical) application of dynamic stable isotope techniques to define biochemical and clinical phenotypes of inherited metabolic diseases associated with hypoglycemia. According to the textbooks, individuals with glycogen storage disease type I (GSD I) display the most severe hypoglycemia/fasting intolerance. In this review, three dynamic methods are discussed which may be considered during both diagnostic work-up and monitoring of children with hypoglycemia: 1) functional in vivo tests; 2) in vivo metabolic profiling by continuous glucose monitoring (CGM); 3) stable isotope techniques. Future applications and benefits of dynamic methods in children with hypoglycemia are also discussed.

Validity of continuous glucose monitoring for categorizing glycemic responses to diet: implications for use in personalized nutrition

BACKGROUND

Continuous glucose monitor (CGM) devices enable characterization of individuals' glycemic variation. However, there are concerns about their reliability for categorizing glycemic responses to foods that would limit their potential application in personalized nutrition recommendations.

OBJECTIVES

We aimed to evaluate the concordance of 2 simultaneously worn CGM devices in measuring postprandial glycemic responses.

METHODS

Within ZOE PREDICT (Personalised Responses to Dietary Composition Trial) 1, 394 participants wore 2 CGM devices simultaneously [n = 360 participants with 2 Abbott Freestyle Libre Pro (FSL) devices; n = 34 participants with both FSL and Dexcom G6] for ≤14 d while consuming standardized (n = 4457) and ad libitum (n = 5738) meals. We examined the CV and correlation of the incremental area under the glucose curve at 2 h (glucoseiAUC0-2 h). Within-subject meal ranking was assessed using Kendall τ rank correlation. Concordance between paired devices in time in range according to the American Diabetes Association cutoffs (TIRADA) and glucose variability (glucose CV) was also investigated.

RESULTS

The CV of glucoseiAUC0-2 h for standardized meals was 3.7% (IQR: 1.7%-7.1%) for intrabrand device and 12.5% (IQR: 5.1%-24.8%) for interbrand device comparisons. Similar estimates were observed for ad libitum meals, with intrabrand and interbrand device CVs of glucoseiAUC0-2 h of 4.1% (IQR: 1.8%-7.1%) and 16.6% (IQR: 5.5%-30.7%), respectively. Kendall τ rank correlation showed glucoseiAUC0-2h-derived meal rankings were agreeable between paired CGM devices (intrabrand: 0.9; IQR: 0.8-0.9; interbrand: 0.7; IQR: 0.5-0.8). Paired CGMs also showed strong concordance for TIRADA with a intrabrand device CV of 4.8% (IQR: 1.9%-9.8%) and an interbrand device CV of 3.2% (IQR: 1.1%-6.2%).

CONCLUSIONS

Our data demonstrate strong concordance of CGM devices in monitoring glycemic responses and suggest their potential use in personalized nutrition.This trial was registered at clinicaltrials.gov as NCT03479866.

Glycogen Storage Disease Type Ia: Current Management Options, Burden and Unmet Needs

Glycogen storage disease type Ia (GSDIa) is caused by defective glucose-6-phosphatase, a key enzyme in carbohydrate metabolism. Affected individuals cannot release glucose during fasting and accumulate excess glycogen and fat in the liver and kidney, putting them at risk of severe hypoglycaemia and secondary metabolic perturbations. Good glycaemic/metabolic control through strict dietary treatment and regular doses of uncooked cornstarch (UCCS) is essential for preventing hypoglycaemia and long-term complications. Dietary treatment has improved the prognosis for patients with GSDIa; however, the disease itself, its management and monitoring have significant physical, psychological and psychosocial burden on individuals and parents/caregivers. Hypoglycaemia risk persists if a single dose of UCCS is delayed/missed or in cases of gastrointestinal intolerance. UCCS therapy is imprecise, does not treat the cause of disease, may trigger secondary metabolic manifestations and may not prevent long-term complications. We review the importance of and challenges associated with achieving good glycaemic/metabolic control in individuals with GSDIa and how this should be balanced with age-specific psychosocial development towards independence, management of anxiety and preservation of quality of life (QoL). The unmet need for treatment strategies that address the cause of disease, restore glucose homeostasis, reduce the risk of hypoglycaemia/secondary metabolic perturbations and improve QoL is also discussed.

A retrospective in-depth analysis of continuous glucose monitoring datasets for patients with hepatic glycogen storage disease: Recommended outcome parameters for glucose management

Continuous glucose monitoring (CGM) systems have great potential for real-time assessment of glycemic variation in patients with hepatic glycogen storage disease (GSD). However, detailed descriptions and in-depth analysis of CGM data from hepatic GSD patients during interventions are scarce. This is a retrospective in-depth analysis of CGM parameters, acquired in a continuous, real-time fashion describing glucose management in 15 individual GSD patients. CGM subsets are obtained both in-hospital and at home, upon nocturnal dietary intervention (n = 1), starch loads (n = 11) and treatment of GSD Ib patients with empagliflozin (n = 3). Descriptive CGM parameters, and parameters reflecting glycemic variation and glycemic control are considered useful CGM outcome parameters. Furthermore, the combination of first and second order derivatives, cumulative sum and Fourier analysis identified both subtle and sudden changes in glucose management; hence, aiding assessment of dietary and medical interventions. CGM data interpolation for nocturnal intervals reduced confounding by physical activity and diet. Based on these analyses, we conclude that in-depth CGM analysis can be a powerful tool to assess glucose management and optimize treatment in individual hepatic GSD patients.

Continuous glucose monitoring for hypoglycaemia in children: Perspectives in 2020

Hypoglycaemia in children is a major risk factor for adverse neurodevelopment with rates as high as 50% in hyperinsulinaemic hypoglycaemia (HH). A key part of management relies upon timely identification and treatment of hypoglycaemia. The current standard of care for glucose monitoring is by infrequent fingerprick plasma glucose testing but this carries a high risk of missed hypoglycaemia identification. High-frequency Continuous Glucose Monitoring (CGM) offers an attractive alternative for glucose trend monitoring and glycaemic phenotyping but its utility remains largely unestablished in disorders of hypoglycaemia. Attempts to determine accuracy through correlation with plasma glucose measurements using conventional methods such as Mean Absolute Relative Difference (MARD) overestimate accuracy at hypoglycaemia. The inaccuracy of CGM in true hypoglycaemia is amplified by calibration algorithms that prioritize hyperglycaemia over hypoglycaemia with minimal objective evidence of efficacy in HH. Conversely, alternative algorithm design has significant potential for predicting hypoglycaemia to prevent neuroglycopaenia and consequent brain dysfunction in childhood disorders. Delays in the detection of hypoglycaemia, alarm fatigue, device calibration and current high cost are all barriers to the wider adoption of CGM in disorders of hypoglycaemia. However, machine learning, artificial intelligence and other computer-generated algorithms now offer significant potential for further improvement in CGM device technology and widespread application in childhood hypoglycaemia.

Predominance of the c.648G > T G6PC gene mutation and late complications in Korean patients with glycogen storage disease type Ia

BACKGROUND

Glycogen storage disease (GSD) Ia, caused by mutations in the glucose-6-phosphatase (G6PC) gene, is characterized by hepatomegaly, hypoglycemia, lactic acidosis, dyslipidemia, and hyperuricemia. This study aimed to investigate clinical and molecular features and late complications in Korean patients with GSD Ia.

RESULTS

Fifty-four Korean patients (33 males and 21 females) from 47 unrelated families, who were diagnosed with GSD Ia, based on genetic and biochemical data, between 1999 and 2017, were included in this study. The median age at diagnosis was 3.9 years (range: 5 months to 42 years), and the follow-up period was 8.0 ± 6.8 years. Most patients presented with hepatomegaly during infancy, but hypoglycemic symptoms were not predominant. Genetic analysis showed that all the patients had at least one c.648G > T allele. Homozygous c.648G > T mutations in the G6PC gene were identified in 34 families (72.3%), and compound heterozygotes with c.648G > T were found in the other families. The allele frequency of c.648G > T was 86.2% (81/94), and p.F51S, p.R83H, p.G122D, p.Y128*, p.G222R, and p.T255A were identified. Of 26 adult patients, 14 had multiple hepatic adenomas, and two were diagnosed with hepatocellular carcinoma. Thirteen patients showed renal complications, and seven patients presented gout, despite preventive allopurinol treatment. Twelve patients had osteoporosis, and two patients had pulmonary hypertension. The final heights were 157.9 cm (standard deviation score: - 3.1) in males and 157.8 cm (standard deviation score: - 0.6) in females.

CONCLUSION

In our Korean patients with GSD Ia, the most common mutation in the G6PC gene was c.648G > T, suggesting a founder effect. Because of only mild hypoglycemia, the patients tended to be diagnosed late. Thus, adult patients with GSD Ia eventually developed diverse and serious complications, which indicates a need for careful monitoring and proper management of this disease.

Liver fibrosis during clinical ascertainment of glycogen storage disease type III: a need for improved and systematic monitoring

PURPOSE

In glycogen storage disease type III (GSD III), liver aminotransferases tend to normalize with age giving an impression that hepatic manifestations improve with age. However, despite dietary treatment, long-term liver complications emerge. We present a GSD III liver natural history study in children to better understand changes in hepatic parameters with age.

METHODS

We reviewed clinical, biochemical, histological, and radiological data in pediatric patients with GSD III, and performed a literature review of GSD III hepatic findings.

RESULTS

Twenty-six patients (median age 12.5 years, range 2-22) with GSD IIIa (n = 23) and IIIb (n = 3) were enrolled in the study. Six of seven pediatric patients showed severe fibrosis on liver biopsy (median [range] age: 1.25 [0.75-7] years). Markers of liver injury (aminotransferases), dysfunction (cholesterol, triglycerides), and glycogen storage (glucose tetrasaccharide, Glc₄) were elevated at an early age, and decreased significantly thereafter (p < 0.001). Creatine phosphokinase was also elevated with no significant correlation with age (p = 0.4).

CONCLUSION

Liver fibrosis can occur at an early age, and may explain the decrease in aminotransferases and Glc₄ with age. Our data outlines the need for systematic follow-up and specific biochemical and radiological tools to monitor the silent course of the liver disease process.

Glycemic control and complications in glycogen storage disease type I: Results from the Swiss registry

BACKGROUND

Regular carbohydrate intake to avoid hypoglycemia is the mainstay of dietary treatment in glycogen storage disease type I (GSDI). The aim of this study was to evaluate the quality of dietary treatment and glycemic control in a cohort of GSDI patients, in relation to the presence of typical long-term complications.

METHODS

Data of 25 patients (22 GSD subtype Ia and 3 GSDIb, median age 20y) from the Swiss hepatic glycogen storage disease registry was analyzed cross-sectionally. Frequency and type of hypoglycemia symptoms were assessed prospectively using a structured questionnaire. Diagnostic continuous glucose monitoring (CGM) was performed as part of usual clinical care to assess glycemic control in 14 patients, usually once per year with a mean duration of 6.2 ± 1.1 consecutive days per patient per measurement.

RESULTS

Although maintenance of euglycemia is the primary goal of dietary treatment, few patients (n = 3, 13%) performed capillary blood glucose measurements regularly. Symptoms possibly associated with hypoglycemia were present in 13 patients (57%), but CGM revealed periods of low glucose (<4 mmol/l) in all patients, irrespective of the presence of symptoms. GSDIa patients with liver adenomas (n = 9, 41%) showed a higher frequency and area under the curve (AUC) of low blood glucose than patients without adenomas (frequency 2.7 ± 0.8 vs. 1.5 ± 0.7 per day, AUC 0.11 ± 0.08 vs. 0.03 ± 0.02 mmol/l/d; p < 0.05). Similarly, the presence of microalbuminuria was also associated with the frequency of low blood glucose. Z-Scores of bone density correlated negatively with lactate levels.

CONCLUSION

The quality of glucose control is related to the presence of typical long-term complications in GSDI. Many patients experience episodes of asymptomatic low blood glucose. Regular assessment of glucose control is an essential element to evaluate the quality of treatment, and increasing the frequency of glucose self-monitoring remains an important goal of patient education and motivation. CGM devices may support patients to optimize dietary therapy in everyday life.