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.

Systematic literature review of the epidemiology of glycogen storage disease type 1a

Glycogen storage disease (GSD) type 1a is an inherited autosomal recessive metabolic disease caused by a deficiency in glucose-6-phosphatase activity. The objectives of this research were to systematically review the published literature on the epidemiology of GSD 1a and to assess the performance of reported epidemiology measures in a simulation model. In this systematic literature review 2,539 record titles and abstracts were screened. Of these, only 11 studies contained relevant data on GSD 1a disease epidemiology. Reported disease frequency ranged from 0.085/100,000 to 10.3/100,000 newborns when considering all the GSD literature. When this was narrowed to GSD 1 and GSD 1a, the range was tightened to 0.25-3.02/100,000 and 0.085-4.9/100,000 newborns, respectively. Most of the identified studies counted the number of diagnoses in a defined period and related to the number of births in the same (Dx method) or different time period (DoB method). The simulation model results indicate that in most of the situations, the Dx method provides a closer estimate to the true disease incidence than the DoB method. Despite the scarcity of epidemiology data, the results of this systematic review strongly support that GSD 1a and its parent disease groups (GSD and GSD 1) are rare diseases.

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.

Estimation of Health Utility Scores for Glycogen Storage Disease Type Ia

BACKGROUND

Glycogen Storage Disease Type Ia (GSDIa) is a rare genetic metabolic disorder characterized by hypoglycemia, hepatomegaly, growth failure, and possible seizures/death. Patients frequently consume cornstarch to maintain blood glucose. Evidence demonstrating the impact of GSDIa on health-related quality of life (HRQoL) is lacking. This study aims to understand the burden of GSDIa by obtaining utility values for economic appraisals.

METHODS

A targeted literature review and interviews with experts (n = 4) and caregivers (n = 4) informed the development of health state vignettes describing different GSDIa severities by age and level of hypothetical treatment (i.e., gene therapy) response. Health states reflecting caregivers' experiences were also developed. A convenience sample of the UK general public completed a time trade-off (TTO) exercise. Scores conceptually varied from 0 (dead) to 1 (full health). States were also rated using a visual analog scale (VAS) and the EQ-5D-5L. Data were descriptively summarized.

RESULTS

One hundred participants completed the exercise (male: 48%; mean age: 42 years). Scores were lowest for the adolescent pre-treatment state (TTO = 0.38). Large increments in HRQoL were observed for the response (adult: TTO = 0.86; child: TTO = 0.84) and complete response (adult and child: TTO = 0.94) hypothetical treatment response states. Caregiver values were lowest for the pre-treatment state (TTO = 0.57) and highest for the complete response state (TTO = 0.95). VAS and EQ-5D-5L scores followed a similar pattern.

CONCLUSION

This study found an HRQoL burden on GSDIa patients and caregivers, with potential large improvement from a hypothetical treatment. These findings may be useful for families, clinicians, regulatory agencies, and in therapy economic evaluations.

Glycogen storage disease type 1a in the Ohio Amish

Glycogen storage disease type 1a (GSD1a) is an inborn error of glucose metabolism characterized by fasting hypoglycemia, hepatomegaly, and growth failure. Late complications include nephropathy and hepatic adenomas. We conducted a retrospective observational study on a cohort of Amish patients with GSD1a. A total of 15 patients cared for at a single center, with a median age of 9.9 years (range 0.25–24 years) were included. All patients shared the same founder variant in GCPC c.1039 C > T. The phenotype of this cohort demonstrated good metabolic control with median cohort triglyceride level slightly above normal, no need for continuous overnight feeds, and a higher quality of life compared to a previous GSD cohort. The most frequent complications were oral aversion, gross motor delay, and renal hyperfiltration. We discuss our unique care delivery at a single center that cares for Amish patients with inherited disorders.

A New Perspective on the Quality of Life of Children with Glycogen Storage Diseases

PURPOSE

This study aimed to assess the quality of life (QoL) of children with glycogen storage disease (GSD) and their parents and to determine the impact of myopathies.

METHODS

A prospective case-control study was conducted at the Cairo University Children's Hospital and National Liver Institute, Menoufia University. A promising new style of questionnaire called the Stark Quality of Life Questionnaire was used to assess the quality of life.

RESULTS

Fifty-two children diagnosed with GSD (cases) and 55 age- and sex-matched healthy children (controls) were included. A statistically significant difference was found between cases and controls regarding food intake; mental behavior parameters such as mood, energy, and social contact; and physical behavior parameters such as running and tying shoelaces. Children with myopathies had significantly lower QoL scores in most of the parameters.

CONCLUSION

GSDs alter children and their parents' mental and physical abilities. Lower QoL scores were detected in children with both skeletal myopathy and cardiomyopathy, but the difference was not statistically significant when compared with the children without myopathies.

A retrospective study of eating and psychosocial problems in patients with hepatic glycogen storage diseases and idiopathic ketotic hypoglycemia: Towards a standard set of patient-reported outcome measures

There is a paucity in literature on eating and psychosocial problems in patients with hepatic glycogen storage disease (GSD) and idiopathic ketotic hypoglycemia (IKH), problems that can greatly affect quality of life. This is a monocentre, retrospective, observational mixed method study of patients with hepatic GSD or IKH treated at the Beatrix Children's Hospital Groningen, who had been referred to SeysCentra, a specialist centre for the treatment of eating problems. Additionally, a systematic literature review has been performed to identify instruments to quantify patient-reported outcome measures of psychosocial problems in hepatic GSD patients. Sixteen patients from 12 families were included with ages ranging between 3 and 24 years. Five out of sixteen patients were diagnosed with Avoidant/Restrictive Food Intake Disorder and six patients showed characteristics of this disorder. Fourteen patients experienced sleeping problems, and 11 out of 12 parent couples experienced stress about the illness of their child. We subsequently identified 26 instruments to quantify patient-reported outcome measures for GSD patients. This study demonstrates that GSD patients can develop Avoidant/Restrictive Food Intake Disorder influencing quality of life at multiple domains. The identification of instruments to assess psychosocial wellbeing is an important step towards a standard set of patient-reported outcome measures.

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.

Impact of glycogen storage disease type I on adult daily life: a survey

Background

Glycogen storage disease type I (GSD I) is a rare autosomal recessive disorder of carbohydate metabolism characterized by recurrent hypoglycaemia and hepatomegaly. Management of GSD I is demanding and comprises a diet with defined carbohydrate intake and the use of complex carbohydrates, nocturnal tube feeding or night-time uncooked cornstarch intake, regular blood glucose monitoring and the handling of emergency situations. With improved treatment, most patients nowadays survive into adulthood. Little research has been performed on the impact of GSD I on daily life, especially in adult patients.

Results

In this multi-centre study we assessed the impact of GSD I on adult daily life in 34 GSD I patients (27 GSD Ia, 7 GSD Ib) between 17 and 54 years (median 26 years) using a self-designed questionnaire that specifically focused on different aspects of daily life, such as job situation, social life, sports, travelling, composition of the household, night-time and day-time dietary management and disease monitoring as well as the patient’s attitude towards the disease. At the time of investigation, the majority of patients either attended school or university or were employed, while 3 patients (9%) were out of work. Most patients ranked GSD I as a disease with moderate severity and disease burden. Dietary treatment was considered challenging by many, but the vast majority of patients considered life with GSD I as well-manageable.

Conclusions

Although the management of GSD I poses a significant burden on daily life, most patients live an independent adult life, have a positive attitude towards their disease and seem to cope well with their situation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13023-021-02006-w.

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.

Measuring parent proxy-reported quality of life of 11 rare diseases in children in Zhejiang, China

BACKGROUND

It has become increasingly important to measure the health-related quality of life (HRQoL) of rare diseases in children and adolescents in recent decades. Much attention has been paid to investigate the HROoL of a specific rare disease by self-report in previous studies. This study aimed to evaluate and compare the HROoL of 11 rare diseases in Chinese children by parent proxy-report, to explore the factors associated with HROoL of patients, and to understand the problems of most concern.

METHODS

A total of 651 children aged from 2 to 18 were enrolled from the Children's Hospital Affiliated Zhejiang University in 2018. Their parents completed the parent proxy-report version of the Pediatric Quality of Life Inventory™ 4.0 (PedsQL™ 4.0). Independent samples t-test, one-way ANOVA, or Kruskal-Wallis H test was used to compare HROoL scores between groups. Multilevel linear regression models with random intercept were applied to analyze the relationship between socioeconomic variables and both the total score and subdomain scores.

RESULTS

The total PedsQL scores of Patent ductus arteriosus (PDA), Infantile agranulocytosis, Autoimmune thrombocytopenia (ITP), Polysyndactyly, Hirschsprung disease, Cleft lip and palate, Tetralogy of fallot, Myasthenia gravis, Guillain-barre syndrome, Glycogen storage disease, and Langerhans cell histiocytosis children were 79.65 ± 5.46, 95.88 ± 3.48, 71.39 ± 3.27, 91.77 ± 6.35, 76.18 ± 6.92, 96.33 ± 4.22, 77.85 ± 8.90, 95.99 ± 3.31, 85.77 ± 4.56, 82.97 ± 4.13 and 77.6 ± 5.15, respectively. Age was significantly associated with physical functioning, school functioning, and psychosocial health scores. The household registration place was significantly related to the total score. The most urgent desire of patients was to reduce the overall medical costs.

CONCLUSIONS

This study showed that patients with PDA had the lowest physical functioning score, while patients with ITP scored the lowest in the emotional functioning, social functioning, school functioning, psychosocial health, and total scores. Incentive policies should be further adopted to improve orphan drug availability and reduce the economic burden of rare diseases.

Increased parental anxiety and a benign clinical course: Infants identified with short-chain acyl-CoA dehydrogenase deficiency and isobutyryl-CoA dehydrogenase deficiency through newborn screening in Georgia

The long-term consequences and need for therapy in children with short-chain acyl-CoA dehydrogenase deficiency (SCADD) or isobutyryl-CoA dehydrogenase deficiency (IBDD) identified via newborn screening (NBS) remains controversial. Initial clinical descriptions were severe; however, while most cases identified through NBS have remained asymptomatic, clinical concerns have been raised in these populations. It is not clear whether these children are asymptomatic because of the success of NBS, or because the normal clinical course of these disorders is relatively benign. To evaluate these possibilities in our program, we evaluated the clinical outcomes of children with SCADD or IBDD identified by the Georgia NBS compared to the health status of a healthy age-matched control group. We also assessed parental anxiety during a phone interview both subjectively and objectively using the Pediatric Inventory for Parents (PIP), a validated measure of illness-related parental stress. The general health of 52 SCADD and nine IBDD cases from 2007 to 2016 were compared to the general health of unaffected control children obtained through the Centers for Disease Control and Prevention (CDC) parent listserv. We also collected statements from parents who participated in a phone survey regarding events they experienced during and after their diagnostic process. Overall, the children with SCADD and IBDD had no major health problems. There was no significant difference in cognitive development (p = .207). We identified a slightly higher incidence of reported neonatal hypoglycemia in the SCADD group; two of these occurred in the context of maternal diabetes. All interviewed parents reported extreme anxiety during the diagnostic period and current feelings of uncertainty about their child's future. PIP scores for all six caregivers who responded to that portion of the survey were consistent with some degree of parental stress. The greatest reported stressor was the unknown long-term impact of the illness. All children with SCADD and IBDD had no significant long-term sequelae. The phone interviews revealed substantial parental anxiety about the identification and follow-up of SCADD and IBDD. Based on our findings, the anxiety parents experience may be unwarranted given that we see no disease-associated morbidity or mortality in these children. Consideration should be given to the removal of these conditions from NBS panels, or if that is not possible, clinicians could educate parents on the benign nature of these diagnoses and release them from follow-up without treatment.

Patient and observer reported outcome measures to evaluate health-related quality of life in inherited metabolic diseases: a scoping review

Background

Health-related Quality of Life (HrQoL) is a multidimensional measure, which has gained clinical and social relevance. Implementation of a patient-centred approach to both clinical research and care settings, has increased the recognition of patient and/or observer reported outcome measures (PROMs or ObsROMs) as informative and reliable tools for HrQoL assessment. Inherited Metabolic Diseases (IMDs) are a group of heterogeneous conditions with phenotypes ranging from mild to severe and mostly lacking effective therapies. Consequently, HrQoL evaluation is particularly relevant.

Objectives

We aimed to: (1) identify patient and/or caregiver-reported HrQoL instruments used among IMDs; (2) identify the main results of the application of each HrQoL tool and (3) evaluate the main limitations of HrQoL instruments and study design/methodology in IMDs.

Methods

A scoping review was conducted using methods outlined by Arksey and O’Malley. Additionally, we critically analysed each article to identify the HrQoL study drawbacks.

Results

Of the 1954 studies identified, 131 addressed HrQoL of IMDs patients using PROMs and/or ObsROMs, both in observational or interventional studies. In total, we identified 32 HrQoL instruments destined to self- or proxy-completion; only 2% were disease-specific. Multiple tools (both generic and disease-specific) proved to be responsive to changes in HrQoL; the SF-36 and PedsQL questionnaires were the most frequently used in the adult and pediatric populations, respectively. Furthermore, proxy data often demonstrated to be a reliable approach complementing self-reported HrQoL scores. Nevertheless, numerous limitations were identified especially due to the rarity of these conditions.

Conclusions

HrQoL is still not frequently assessed in IMDs. However, our results show successful examples of the use of patient-reported HrQoL instruments in this field. The importance of HrQoL measurement for clinical research and therapy development, incites to further research in HrQoL PROMs’ and ObsROMs’ creation and validation in IMDs.

Electronic supplementary material

The online version of this article (10.1186/s13023-018-0953-9) contains supplementary material, which is available to authorized users.

Safety issues associated with dietary management in patients with hepatic glycogen storage disease

INTRODUCTION

Hepatic glycogen storage diseases (GSDs) are a group of inherited disorders of carbohydrate metabolism for which dietary management is the cornerstone. Safety and acute complications associated with dietary management have been poorly documented. We hypothesized that safety issues and complications associated with dietary management are prevalent amongst patients with these ultra-rare disorders.

METHODS

A questionnaire was developed consisting of 40 questions and was distributed via eight GSD patient organizations from multiple countries. Respondents were (caregivers of) patients with self-reported hepatic GSD.

RESULTS

249 GSD patients from 26 countries responded with a median age of 14.8 years (range: 0.5-66.1). Although management was considered safe by 71% of patients, 51% reported at least one acute complication associated with dietary management, with a total number of 425 reported complications. Most frequently reported causes were: not waking up by an alarm clock (n = 70), forgetting a meal (n = 57) and infections (n = 43). Most frequently reported complications were: hypoglycemia (n = 112), hospital admissions (n = 79) and drowsiness (n = 74). Most complications occurred before the age of 12 years (82%; 637/774 total number of reported events) and during night time (63%; 340/536). Only 61% (152/249) of the GSD patients reported using a written emergency protocol.

CONCLUSIONS

Safety issues and complications associated with dietary management are prevalently reported by (caregivers of) 249 GSD patients. A discrepancy has been observed between the patient's perspective on safety of dietary management and occurrence of complications as a result of dietary management.

Parenting a Child with Phenylketonuria (PKU): an Interpretative Phenomenological Analysis (IPA) of the Experience of Parents

Phenylketonuria (PKU) is a rare inherited metabolic disorder which can cause neurological damage if left untreated. PKU is identified through newborn screening in developed countries, and treatment begins immediately to prevent these severe consequences. When a child is diagnosed, parents must assume immediate responsibility for the management of PKU and prevention of neurological damage. Quantitative studies have identified significant psychosocial stressors for parents, but little is known about how the parents experience this process. This study aimed to explore the experiences of parents of children with PKU under the age of two. It is the first study to examine these experiences in this way. Seven parents were interviewed about their experiences, and interpretative phenomenological analysis was used to analyse the data. Three main themes were identified: control, striving for normality and acceptance of PKU as a continuum. Links between the themes and processes underpinning the results were explored with relation to existing literature and theories from a clinical psychology perspective. The role of acceptance of PKU was central to the parent's experiences. Clinical implications and suggestions for further research are discussed.

Barriers to drug adherence in the treatment of urea cycle disorders: Assessment of patient, caregiver and provider perspectives

Patients and families living with metabolic disorders face challenging dietary and drug treatment regimens. On the hypothesis that poor palatability, volume and frequency of drug/formula administration contribute to treatment non-adherence and hyperammonemic episodes, a survey was conducted of patient, caregiver (CG) and physician perspectives on treatments used in urea cycle disorders (UCD).

Methods

A paper and online survey assessed experience with UCD medications, medical foods and dietary supplements.

Results

25 physicians, 52 adult patients and 114 CG responded. In 2009, the most common UCD-specific intervention reported by patients included sodium phenylbutyrate (60%), followed by l-citrulline (46%), amino acid medical foods (15%), l-arginine preparations (18%), and sodium benzoate (8%). Only 36% of patients reported experiencing no hyperammonemic episodes in the last 2 years. The most commonly reported cause of hyperammonemic episodes was infection or other acute illnesses, followed by dietary indiscretion, side effects of medications, and drug non-adherence. Most patients, caregivers and physicians (> 75%) ranked nitrogen-scavenging medications, l-citrulline, l-arginine, and medical foods as “effective” or “very effective.” Non-adherence was common (e.g. 18% of patients admitted to missing sodium phenylbutyrate “at least once a week” and “at least one a day”). Barriers to adherence included taste of medications, frequency of drug administration, number of pills, difficulty swallowing pills, side effects, forgetting to take medications, and high cost. Strategies to mitigate the gastrointestinal side effects of medications included the use of gastric tubes and acid reflux medications. Physicians indicated that 25% and 33% of pediatric and adult patients, respectively, were given less than the recommended dose of sodium phenylbutyrate due to concerns of tolerance, administration, and cost.

Conclusions

Despite positive views of their effectiveness, respondents found medications, medical foods and dietary supplements difficult to take and viewed adherence as inadequate, thus contributing to hyperammonemic episodes.

Parent Coping and the Behavioural and Social Outcomes of Children Diagnosed with Inherited Metabolic Disorders

OBJECTIVE

To explore the level of coping and management of parents of children with inherited metabolic disorders (IMD) and the relationship with children's cognitive, behavioural and social functioning.

METHODS

Parents of children (n = 22) with confirmed IMD (glutaric aciduria type I, methylmalonic aciduria, propionic aciduria, isovaleric aciduria, glycogen storage disease, maple syrup urine disease, ornithine transcarbamylase or very long-chain acyl-CoA dehydrogenase deficiency) completed standardised questionnaires regarding psychological distress, coping and family management. Children completed cognitive assessments and parents rated their behavioural and social functioning on standardised questionnaires. Scores were compared with normative data.

RESULTS

Most parents were coping well; 4/22 reported high levels of psychological distress. Exploratory analysis found that parent coping variables were correlated to the child's internalising symptoms, whereas family management was related to children's externalising behaviours and social skills. No relationship was found between parent variables and cognitive functioning.

CONCLUSIONS

Parental coping and family management impact on the child's internalising symptoms and externalising behaviours, respectively. Early identification of issues in these domains may enhance referral for therapeutic interventions and family support programmes.

Safety and Efficacy of Chronic Extended Release Cornstarch Therapy for Glycogen Storage Disease Type I

BACKGROUND

Glycogen storage disease type I (GSD I) causes severe hypoglycemia during periods of fasting since both glycogenolysis and gluconeogenesis are impaired. Primary treatment in North America consists of cornstarch therapy every 3-4 h. Waxy maize extended release cornstarch was introduced for maintaining overnight glucose concentrations, but no studies have assessed long-term safety and efficacy of the product.

OBJECTIVE

To demonstrate the safety and efficacy of modified cornstarch in GSD I.

DESIGN

An open-label overnight trial of extended release cornstarch was performed. Subjects with a successful trial (optimal metabolic control 2 or more hours longer than with traditional cornstarch) were given the option of continuing into the chronic observational phase. Subjects were assessed biochemically at baseline and after 12 months.

RESULTS

Of the 106 subjects (93 GSD Ia/13 GSD Ib), efficacy was demonstrated in 82 patients (88%) with GSD Ia and 10 patients (77%) with GSD Ib. The success rate for extending fasting was 95% for females and 78% for males. Of the patients who entered the longitudinal phase, long-term data are available for 44 subjects. Mean duration of fasting on traditional cornstarch prior to study for the cohort was 4.1 and 7.8 h on the extended release cornstarch (P < 0.001). All laboratory markers of metabolic control have remained stable in the chronically treated patients.

CONCLUSION

Extended release cornstarch appears to improve the quality of life of patients with GSD I without sacrificing metabolic control. Avoiding the overnight dose of cornstarch should enhance safety in this population.

Diagnosis and management of glycogen storage disease type I: a practice guideline of the American College of Medical Genetics and Genomics

PURPOSE

Glycogen storage disease type I (GSD I) is a rare disease of variable clinical severity that primarily affects the liver and kidney. It is caused by deficient activity of the glucose 6-phosphatase enzyme (GSD Ia) or a deficiency in the microsomal transport proteins for glucose 6-phosphate (GSD Ib), resulting in excessive accumulation of glycogen and fat in the liver, kidney, and intestinal mucosa. Patients with GSD I have a wide spectrum of clinical manifestations, including hepatomegaly, hypoglycemia, lactic acidemia, hyperlipidemia, hyperuricemia, and growth retardation. Individuals with GSD type Ia typically have symptoms related to hypoglycemia in infancy when the interval between feedings is extended to 3–4 hours. Other manifestations of the disease vary in age of onset, rate of disease progression, and severity. In addition, patients with type Ib have neutropenia, impaired neutrophil function, and inflammatory bowel disease. This guideline for the management of GSD I was developed as an educational resource for health-care providers to facilitate prompt, accurate diagnosis and appropriate management of patients.

METHODS

A national group of experts in various aspects of GSD I met to review the evidence base from the scientific literature and provided their expert opinions. Consensus was developed in each area of diagnosis, treatment, and management.

RESULTS

This management guideline specifically addresses evaluation and diagnosis across multiple organ systems (hepatic, kidney, gastrointestinal/nutrition, hematologic, cardiovascular, reproductive) involved in GSD I. Conditions to consider in the differential diagnosis stemming from presenting features and diagnostic algorithms are discussed. Aspects of diagnostic evaluation and nutritional and medical management, including care coordination, genetic counseling, hepatic and renal transplantation, and prenatal diagnosis, are also addressed.

CONCLUSION

A guideline that facilitates accurate diagnosis and optimal management of patients with GSD I was developed. This guideline helps health-care providers recognize patients with all forms of GSD I, expedite diagnosis, and minimize adverse sequelae from delayed diagnosis and inappropriate management. It also helps to identify gaps in scientific knowledge that exist today and suggests future studies.

Longitudinal study of neuropsychological functioning and internalizing symptoms in youth with spina bifida: social competence as a mediator

OBJECTIVE

To examine the longitudinal relationship between neuropsychological functioning and internalizing symptoms, as mediated by social competence in youth with spina bifida (SB).

METHODS

A total of 111 youth (aged 8-15 years, M = 11.37) with SB, their parents, and teachers completed questionnaires regarding attention, social competence, and internalizing symptoms. Youth also completed a battery of neuropsychological tests.

RESULTS

An indirect-only mediation model revealed that social competence mediated the relation between neuropsychological functioning and subsequent levels of teacher-reported internalizing symptoms, but not parent or youth report of internalizing symptoms. Specifically, better neuropsychological functioning was associated with better social competence, which, in turn, predicted fewer internalizing symptoms 2 years later.

CONCLUSIONS

Youth with SB with lower levels of neuropsychological functioning may be at risk for poorer social competence and, as a result, greater internalizing symptoms. Interventions that promote social competence, while being sensitive to cognitive capacities, could potentially alleviate or prevent internalizing symptoms in these youth.

A pilot longitudinal study of the use of waxy maize heat modified starch in the treatment of adults with glycogen storage disease type I: a randomized double-blind cross-over study

Background

Uncooked corn-starch (UCCS) has been the mainstay of therapy for the hepatic glycogen storage diseases (GSD) but is not always effective. A new starch (WMHMS) has demonstrated a more favourable short-term metabolic profile.

Objective

To determine efficacy and safety of a new uncooked starch (WMHMS) compared to UCCS over 16 weeks treatment with each.

Method

A double-blind cross-over study of 10 adults (aged 16 – 38 years, six male) with GSD Ia and Ib. After an individualised fast, subjects were randomised to take a 50 g starch-load of either WMHMS or UCCS. Starch-loads terminated when blood glucose was < 3.0 mmol/L or the subject felt subjectively hypoglycaemic. Anonymous biochemical profiles were assessed by 2 investigators and a starch administration schedule recommended. Each starch was delivered in coded sachets and intake was monitored for the following 16 weeks. After a washout period, the protocol was repeated with the alternative product.

Results

4 subjects failed to establish therapy on the cross-over limb. Data from 7 paired starch load showed: longer median fasting duration with WMHMS (7.5 versus 5 hours; p = 0.023), slower decrease in the glucose curve (0.357 versus 0.632 mmol/hr p = 0.028) and less area under insulin curves for the first 4 hours (p = 0.03). Two of six subjects took 50% or less WMHMS compared to UCCS and one took more. Plasma triglycerides, cholesterol and uric acid were unchanged after each study phase.

Conclusion

WMHMS leads to significant reduction in insulin release and reduced starch use in some GSD patients.

Chinese family management of chronic childhood conditions: a cluster analysis

PURPOSE

This study compared the management of chronic childhood conditions in Chinese families and identified predictors of management style.

DESIGN AND METHOD

A survey was conducted in 2008-2009 on a convenience sample of 387 caregivers of children with chronic conditions.

RESULTS

Six family management styles (FMSs) were identified: accomplished, uncertain managing, joint managing, managing with difficulty, struggling, and competent managing. The FMSs were related to the functioning of the family and the child. Changes in parents' employment, geographic location, and diagnosis predicted family placement in a cluster.

PRACTICE IMPLICATIONS

Understanding Chinese FMSs will further aid in providing culturally appropriate family-centered care. Awareness of the predictors of FMSs can assist nurses in detecting which families need more help.

Quality of life in adult patients with glycogen storage disease type I: results of a multicenter italian study

BACKGROUND

Glycogen storage disease type I (GSD I) is a chronic metabolic disease that requires a lifelong strict dietetic treatment to avoid hypoglycemia and can lead to severe complications during adult age. Impaired quality of life (QoL) has been reported in affected children, but this aspect has not been previously investigated in adults.

OBJECTIVE

To assess QoL in adult patients with GSD I.

PATIENTS AND METHODS

Italian patients with GSD type Ia and Ib, who were 16 years or older, were asked to complete the SF-36 questionnaire, assessing their QoL. Data on demographic characteristics and clinical history were collected from clinical records and interviews.

RESULTS

Thirty-eight patients (22 females, 16 males; 27 with GSD Ia, 11 with GSD Ib, median age 26.5 years) completed the SF-36 questionnaire. Overall, when compared to normal values, patients with GSD I had lower median scores in general health perception and social functioning, but better median scores for bodily pain and mental health. Patients with GSD Ib had a lower Z-score than GSD Ia patients for emotional health problems. Male patients showed better Z-scores in physical functioning, general health perception, and social functioning when compared to females. Emotional health problems Z-score was lower in nephropathic patients.

CONCLUSION

QoL can be impaired in adult patients with GSD I. The results of this study show that patients with GSD type Ib, women, and those with renal complications are more likely to experience a poorer QoL.

[Construction and validation of an evaluation tool of sexual health using self-administered questionnaires for an application to metabolic diseases]

AIM

To elaborate and validate in general population a survey built with self-administered questionnaires in French about evaluation of sexual health for an application to men and women with metabolic disease.

MATERIALS AND METHODS

Study built with four questionnaires (socio-familial environment [MSPSS scale], self-esteem [Rosenberg scale], anxiety and depression scale [Sigmund and Snaith scale], and male [BISF-M] or female [BISF-W] sexuality) translated in French and distributed to 232 men and 260 women.

RESULTS

Hundred and eleven men aged 18 to 56 years and 142 women aged 20 to 60 years answered the self-administered questionnaire. Analysis showed several links between self-esteem, anxiety and depression and the different domains of male sexuality, justifying their association. Comparison between men and women confirmed the differences of sexual approach between the two sexes.

CONCLUSION

Results in our population were concordant with those already reported in literature, indicating the validity and the reliability of our questionnaire and its multiparametric approach. Data obtained in this population will allow to use this multiparametric tool with patients affected by a metabolic disease.

The experiences of living with a sibling who stutters: a preliminary study

Stuttering impacts on the child in a variety of ways, notably in terms of communicative impairment and psychosocial impact. In addition, the stuttering disorder has a holistic impact, affecting those with whom the child who stutters lives. Within the family constellation, the closest person to the individual who stutters is often their sibling. This study investigated the experiences of fluent siblings of children who stutter to examine the impact that stuttering may have on their lives. A mixed methods research design incorporated qualitative semi-structured interviews and quantitative questionnaires. The results of the qualitative investigation revealed four aspects of children's lives that were affected by having a sibling who stuttered: the relationship between siblings, the impact on the fluent sibling, the impact on the parent relationship with both children, and the impact on the sibling's relationship with others. Findings revealed that siblings of children who stutter exhibited strongly negative emotions, and differing levels of responsibility associated with their involvement in the actual stuttering management programme. Furthermore, for the fluent sibling, secondary to having a brother or sister who stuttered, communication with and attention from their parents was variable. The results of the quantitative component of the study revealed children who stutter and their siblings demonstrated significantly greater closeness, and concurrently, increased conflict and status disparity than did the control fluent sibling dyads. The parents of the experimental sibling dyads also demonstrated significantly greater partiality towards a child, namely the child who stuttered, than did the parents of the control sibling dyads.

EDUCATIONAL OBJECTIVES

The reader will be able to: (1) identify the themes associated with having a sibling who stutters; (2) identify how the quality of the sibling relationship differs between sibling dyads that do and do not consist of a sibling who stutters; and (3) discuss the clinical implications of the results with regards to working with children who stutter and their families.

Young adults with MSUD and their transition to adulthood: psychosocial issues

Maple Syrup Urine Disease (MSUD) is an autosomal recessive condition with an incidence of 1 in 185,000 births worldwide. Regardless of the type of MSUD, treatment includes immediate and lifelong dietary restriction of isoleucine, leucine and valine. There is little known about the psychosocial impact of MSUD on the developmental milestones of emerging adulthood. We used a qualitative case study approach to explore the human experiences of MSUD on young adults (n = 8) and parents (n = 8). All participants were administered a semi-structured, qualitative interview as well as quantitative measures. Six core themes emerged: 1) lifelong strain of dietary management; 2) social isolation from peers and impact on dating; 3) impact of MSUD on academics and employment; 4) medical experiences and transition to adult care; 5) impact on family functioning; and 6) positive effects and growth. The results of this investigation highlight and expand awareness of the psychological and social needs of young adults with MSUD. This study calls for a collaborative, multidisciplinary effort in the treatment of these patients and their families.

Dietary dilemmas in the management of glycogen storage disease type I

Over the last 50 years, understanding the biochemical bases of glycogen storage disease type I has led to vastly improved survival and health outcomes but the management still centres around an extremely intensive dietary regimen. Patients' metabolic profiles are really determined by the whole of the diet and it can be very difficult to adjust therapy accordingly. In an iso-energetic diet with reference total energy intake, high carbohydrate intake could compromise other macro- and micro-nutrients; if carbohydrates are not restricted then total energy intake is excessive. The quality of the macronutrient such as the glycemic index of carbohydrate, the type of sugar and the proportion of medium-chain triglyceride and essential fatty acids also has a bearing on an individual's long-term metabolic control with potential clinical correlates. These factors as well as the different requirements between individuals and within individuals as they get older mean that the management of glycogen storage disease type I is particularly fraught. Regular clinical and dietary review is imperative as patients grow, ensuring adequate but not excessive low glycaemic index carbohydrate intake, appropriate dynamic biochemical profiles and suitable age appropriate eating patterns. Without diligent management, and education that empowers the patient, these individuals can struggle in adult life.

Quality of life in rare genetic conditions: a systematic review of the literature

Quality of life (QoL) refers to an individual's sense of overall well-being encompassing physical, psychological, emotional, social, and spiritual dimensions. Although genetics healthcare providers strive to promote patient well-being, and the term QoL is often invoked to refer to this outcome, there is lack of clarity as to what actually constitutes QoL from the patient's perspective. This systematic literature review aims to summarize and integrate research findings to help elucidate how healthcare providers can more effectively enhance the QoL of patients affected with rare genetic conditions. Eligible studies were those that measured QoL as a primary outcome variable using a validated, multi-dimensional scale. Detailed criteria were used to rate quality of design, methodology, and analytic rigor. Fifty-eight studies were selected for inclusion in the review, and a narrative synthesis of the data was performed. A central theme emerging from the literature is that, although genetic conditions have the potential to have significant negative consequences for individuals' lives, having a genetic condition does not necessarily entail poor QoL. Evidence demonstrates that factors beyond the physical manifestations of the disease, such as psychological well-being, coping, and illness perceptions, influence QoL and may serve as potent targets for intervention. The field of research on QoL in rare genetic conditions will be advanced by uniting around a clear conceptualization of QoL and using more rigorous methodology with comprehensive measures of global QoL.