Nephrolithiasis, hypocitraturia, and a distal renal tubular acidification defect in type 1 glycogen storage disease

Clinical and biochemical footprints of inherited metabolic diseases. XIV. Metabolic kidney diseases

Kidney disease is a global health burden with high morbidity and mortality. Causes of kidney disease are numerous, extending from common disease groups like diabetes and arterial hypertension to rare conditions including inherited metabolic diseases (IMDs). Given its unique anatomy and function, the kidney is a target organ in about 10% of known IMDs, emphasizing the relevant contribution of IMDs to kidney disease. The pattern of injury affects all segments of the nephron including glomerular disease, proximal and distal tubular damage, kidney cyst formation, built-up of nephrocalcinosis and stones as well as severe malformations. We revised and updated the list of known metabolic etiologies associated with kidney involvement and found 190 relevant IMDs. This represents the 14th of a series of educational articles providing a comprehensive and revised list of metabolic differential diagnoses according to system involvement.

Glycogen storage diseases: An update

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

Incomplete distal renal tubular acidosis in children

AIM

To describe incomplete distal renal tubular acidosis (iDRTA) in paediatric patients, a term used for the diagnosis of patients who do not develop spontaneous overt metabolic acidosis but are unable to acidify the urine in response to an ammonium chloride load.

METHODS

Tests used to explore urinary acidification were revised. In addition, publications in English extracted from 161 entries yielded by a PubMed database search, using 'incomplete distal renal tubular acidosis' as keyword, were reviewed.

RESULTS

Incomplete distal renal tubular acidosis has mostly been identified in adults with autoimmune diseases, nephrolithiasis, nephrocalcinosis and/or osteopenia. iDRTA has been reported in few paediatric patients with rickets, congenital abnormalities of kidney and urological tract and/or growth failure. The pathophysiological mechanisms potentially responsible for the defect of urinary acidification are discussed as well as the clinical and biochemical findings of iDRTA described in children.

CONCLUSION

The presentation of iDRTA in children differs from adults. The clinical and biochemical features of iDRTA are not well characterised in paediatric patients. The detection of iDRTA in groups of population such as heterozygous carriers of primary DRTA gene mutations and children with hypocitraturia or hypercalciuria might be of clinical interest to better know the pathophysiology and natural history of iDRTA.

Kidney and Metabolic Phenotypes in Glycogen Storage Disease Type-I Patients

Patients and Methods: A retrospective chart review of 32 GSD- I patients, followed at the American University of Beirut Medical Center, between 2007 and 2018 was conducted. Diagnosis was confirmed by enzymatic and/or genetic studies. Clinical presentation, growth, and kidney outcome were assessed. All patients were evaluated for body mass index, blood parameters of metabolic control including uric acid, alanine, lactic acid, and triglycerides in blood. Kidney evaluation included creatinine clearance, microalbuminuria, citraturia, and calciuria as well as urine microalbumin/creatinine ratio. Results: Almost one third of GSD-I patients developed microalbuminuria. This was detected below 7 months of age in 36% of patients who required early treatment with ACEI with significant reduction in albuminuria. Kidney stones were present in 6% and were associated with hypercalciuria and hypocitraturia. Poor metabolic control reflected by hyperuricemia, lactic acidosis, and hyperalaninemia were noted only in patients who developed microalbuminuria. Conclusion: Glomerular injury may appear in early infancy in poorly controlled patients. Adequate metabolic control and ACEI therapy may improve kidney outcome in GSD I patients. Plasma alanine appears to be a promising and reliable marker reflecting metabolic control in GSD-I patients.

Review of combined liver and kidney transplantation in children

In this review, we focused on CLKT with regard to indication, results, outcome, and future developments. PH1 is one of the most common diagnoses for adult and pediatric patients qualifying for CLKT. The other major indication for combined transplantation is ARPKD. CLKT appears to be superior to sequential liver and kidney transplantation in the majority of patients and overall results following CLKT are now good, even in small children. Clinical observations suggest that there is an immunological advantage of CLKT in comparison with isolated liver or kidney transplantation. More clinical studies are necessary to identify the best candidates for CLKT while the availability of donor organs is low.

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.

[Renal involvement in glycogen storage disease type 1: Practical issues]

AIM

To investigate risk factors of renal complications in glycogen storage disease type I, in order to identify practical implications for renal preservation.

METHODS

A retrospective study of 38 patients with glycogen storage disease type I.

RESULTS

The patients studied were 8.6 years old in average (1.5 to 22 years) and were followed during 7.4 ± 4.5 years. Hypercalciuria was detected in 23 patients and was related to acidosis (P=0.028), higher lactate levels (5.9 ± 3.5 versus 3.7 ± 1.7 mmol/L; P=0.013) and smaller height (-2.1 ± 1.5 SD versus -0.8 ± 1.5 SD; P=0.026). Urolithiasis was diagnosed in 7 cases. Glomerular disease (19/38) was more frequent in cases with severe hypertriglyceridemia (P=0.042) and occurred at an older age (P=0.007). Microalbuminuria occurred in 15/31 cases; ACE inhibitors were prescribed in only 8 cases. The frequency of renal complications did not differ according to the diet group (continuous enteral feeding or uncooked starch). Logistic regression concluded as risk factors: lactic acidosis for tubular disease and age>10 years for glomerular disease.

CONCLUSIONS

Renal involvement is common in glycogen storage disease type I patients. Tubular abnormalities are precocious, related to lactic acidosis and may be detected by monitoring of urinary calcium. Glomerular hyperfiltration is the first stage of a progressive glomerular disease and is related to age. Practical implications for renal preservation are discussed based on our results and literature.

Glycogen Storage Disease type 1a - a secondary cause for hyperlipidemia: report of five cases

BACKGROUND AND AIMS

Glycogen storage disease type Ia (GSD Ia) is a rare metabolic disorder, caused by deficient activity of glucose-6-phosphatase-α. It produces fasting induced hypoglycemia and hepatomegaly, usually manifested in the first semester of life. Besides, it is also associated with growth delay, anemia, platelet dysfunction, osteopenia and sometimes osteoporosis. Hyperlipidemia and hyperuricemia are almost always present and hepatocellular adenomas and renal dysfunction frequent late complications.

METHODS

The authors present a report of five adult patients with GSD Ia followed in internal medicine appointments and subspecialties.

RESULTS

Four out of five patients were diagnosed in the first 6 months of life, while the other one was diagnosed in adult life after the discovery of hepatocellular adenomas. In two cases genetic tests were performed, being identified the missense mutation R83C in one, and the mutation IVS4-3C > G in the intron 4 of glucose-6-phosphatase gene, not previously described, in the other. Growth retardation was present in 3 patients, and all of them had anemia, increased bleeding tendency and hepatocellular adenomas; osteopenia/osteoporosis was present in three cases. All but one patient had marked hyperlipidemia and hyperuricemia, with evidence of endothelial dysfunction in one case and of brain damage with refractory epilepsy in another case. Proteinuria was present in two cases and end-stage renal disease in another case. There was a great variability in the dietary measures; in one case, liver transplantation was performed, with correction of the metabolic derangements.

CONCLUSIONS

Hyperlipidemia is almost always present and only partially responds to dietary and drug therapy; liver transplantation is the only definitive solution. Although its association with premature atherosclerosis is rare, there have been reports of endothelial dysfunction, raising the possibility for increased cardiovascular risk in this group of patients. Being a rare disease, no single metabolic center has experience with large numbers of patients and the recommendations are based on clinical experience more than large scale studies.

Nephrocalcinosis and urolithiasis in children

The incidence of adult urolithiasis has increased significantly in industrialized countries over the past decades. Sound incidence rates are not available for children, nor are they known for nephrocalcinosis, which can appear as a single entity or together with urolithiasis. In contrast to the adult kidney stone patient, where environmental factors are the main cause, genetic and/or metabolic disorders are the main reason for childhood nephrocalcinosis and urolithiasis. While hypercalciuria is considered to be the most frequent risk factor, several other metabolic disorders such as hypocitraturia or hyperoxaluria, as well as a variety of renal tubular diseases, e.g., Dent's disease or renal tubular acidosis, have to be ruled out by urine and/or blood analysis. Associated symptoms such as growth retardation, intestinal absorption, or bone demineralization should be evaluated for diagnostic and therapeutic purposes. Preterm infants are a special risk population with a high incidence of nephrocalcinosis arising from immature kidney, medication, and hypocitraturia. In children, concise evaluation will reveal an underlying pathomechanism in >75% of patients. Early treatment reducing urinary saturation of the soluble by increasing fluid intake and by providing crystallization inhibitors, as well as disease-specific medication, are mandatory to prevent recurrent kidney stones and/or progressive nephrocalcinosis, and consequently deterioration of renal function.

Stone forming risk factors in patients with type Ia glycogen storage disease

PURPOSE

Patients with type Ia glycogen storage disease have an increased recurrent nephrolithiasis rate. We identified stone forming risk factors in patients with type Ia glycogen storage disease vs those in stone formers without the disease.

MATERIALS AND METHODS

Patients with type Ia glycogen storage disease were prospectively enrolled from our metabolic clinic. Patient 24-hour urine parameters were compared to those in age and gender matched stone forming controls.

RESULTS

We collected 24-hour urine samples from 13 patients with type Ia glycogen storage disease. Average +/- SD age was 27.0 +/- 13.0 years and 6 patients (46%) were male. Compared to age and gender matched hypocitraturic, stone forming controls patients had profound hypocitraturia (urinary citrate 70 vs 344 mg daily, p = 0.009). When comparing creatinine adjusted urinary values, patients had profound hypocitraturia (0.119 vs 0.291 mg/mg creatinine, p = 0.005) and higher oxalate (0.026 vs 0.021 mg/mg creatinine, p = 0.038) vs other stone formers.

CONCLUSIONS

Patients with type Ia glycogen storage disease have profound hypocitraturia, as evidenced by 24-hour urine collections, even compared to other stone formers. This may be related to a recurrent nephrolithiasis rate greater than in the overall population. These findings may be used to support different treatment modalities, timing and/or doses to prevent urinary lithiasis in patients with type Ia glycogen storage disease.

Renal function in glycogen storage disease type I, natural course, and renopreservative effects of ACE inhibition

BACKGROUND AND OBJECTIVES

Renal failure is a major complication in glycogen storage disease type I (GSD I). We studied the natural course of renal function in GSD I patients. We studied differences between patients in optimal and nonoptimal metabolic control and possible renoprotective effects of angiotensin converting enzyme inhibition.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Thirty-nine GSD I patients that visited our clinic were studied. GFR and effective renal plasma flow (ERPF) were measured by means of I(125) iothalamate and I(131) hippuran clearance and corrected for body surface area. Microalbuminuria was defined as >2.5 mg albumin/mmol creatinine and proteinuria as >0.2 g protein per liter. Optimal metabolic control was present when blood glucoses were >3.5 mmol/L, urine lactate/creatinine ratios <0.06 mmol/mmol, triglycerides <6.0 mmol/L, and uric acid concentrations <450 micromol/L.

RESULTS

Quadratic regression analysis showed a biphasic pattern in the course of GFR and ERPF related to age. Microalbuminuria was observed significantly less frequently in the patients with optimal metabolic control compared with the patients with nonoptimal metabolic control. A significant decrease in GFR was observed after starting ACE inhibition.

CONCLUSIONS

This study describes a biphasic pattern of the natural course of GFR and ERPF in GSD I patients, followed by the development of microalbuminuria and proteinuria. Optimal metabolic control has a renoprotective effect on the development of microalbuminuria and proteinuria in GSD I patients. Treatment with ACE inhibitors significantly decreases the GFR, especially in GSD I patients with glomerular hyperfiltration.

Nutritional therapy for glycogen storage diseases

Glycogen storage diseases (GSDs) are a group of inherited disorders characterized by enzyme defects that affect the glycogen synthesis and degradation cycle, classified according to the enzyme deficiency and the affected tissue. The understanding of GSD has increased in recent decades, and nutritional management of some GSDs has allowed better control of hypoglycemia and metabolic complications. However, growth failure and liver, renal, and other complications are frequent problems in the long-term outcome. Hypoglycemia is the main biochemical consequence of GSD type I and some of the other GSDs. The basis of dietary therapy is nutritional manipulation to prevent hypoglycemia and improve metabolic dysfunction, with the use of continuous nocturnal intragastric feeding or cornstarch therapy at night and foods rich in starches with low concentrations of galactose and fructose during the day and to prevent hypoglycemia during the night.

Glycogen storage diseases: new perspectives

Glycogen storage diseases (GSD) are inherited metabolic disorders of glycogen metabolism. Different hormones, including insulin, glucagon, and cortisol regulate the relationship of glycolysis, gluconeogenesis and glycogen synthesis. The overall GSD incidence is estimated 1 case per 20000-43000 live births. There are over 12 types and they are classified based on the enzyme deficiency and the affected tissue. Disorders of glycogen degradation may affect primarily the liver, the muscle, or both. Type Ia involves the liver, kidney and intestine (and Ib also leukocytes), and the clinical manifestations are hepatomegaly, failure to thrive, hypoglycemia, hyperlactatemia, hyperuricemia and hyperlipidemia. Type IIIa involves both the liver and muscle, and IIIb solely the liver. The liver symptoms generally improve with age. Type IV usually presents in the first year of life, with hepatomegaly and growth retardation. The disease in general is progressive to cirrhosis. Type VI and IX are a heterogeneous group of diseases caused by a deficiency of the liver phosphorylase and phosphorylase kinase system. There is no hyperuricemia or hyperlactatemia. Type XI is characterized by hepatic glycogenosis and renal Fanconi syndrome. Type II is a prototype of inborn lysosomal storage diseases and involves many organs but primarily the muscle. Types V and VII involve only the muscle.

Urolithiasis and psoas abscess in a 2-year-old boy with type 1 glycogen storage disease

We report on a pyogenic psoas abscess secondary to an impacted calcium oxalate ureteric stone in a 2-year-old boy with glycogen storage disease type 1 (GSD-1). The patient had a drainage of the abscess through a flank incision followed by percutaneous nephrostomy and open ureterolithotomy. Metabolic acidosis, hyperuricemia, hypocitraturia, and hypercalciuria appear to be significant in the pathogenesis of urolithiasis in patients with GSD-1. Regular ultrasonography of the abdomen along with optimal metabolic control may delay or prevent urolithiasis and its complications in GSD-1 patients.

Renal sonographic findings of type I glycogen storage disease in infancy and early childhood

BACKGROUND

Type I glycogen storage disease (GSD-I) is an inherited disorder affecting glycogenolysis and gluconeogenesis. The characteristic manifestations are hepatomegaly, hypoglycemia, hyperlacticacidemia, hyperuricemia, and hyperlipidemia. Renal disease is regarded as a long-term complication and is reported mainly in older patients.

OBJECTIVE

We report the renal manifestations and renal ultrasonographic findings of GSD-I in infancy and early childhood in order to assess the role of renal sonography in the diagnosis of GSD-I.

MATERIALS AND METHODS

We retrospectively reviewed our hospital's database for patients with GSD-I from January 1993 to September 2004. The records of five patients were reviewed for this study. These five patients were diagnosed when they were younger than 3 years old. Data extracted from the charts included the initial extrarenal and renal manifestations, laboratory data, and imaging studies. We analyzed the indications for, and results of, renal sonography.

RESULTS

In addition to the clinical presentations and laboratory abnormalities, all five children had nephromegaly and increased echogenicity on ultrasonography on their first visit, although only a minor degree of tubular dysfunction was noted clinically. Three of these five patients had nephrocalcinosis or renal stones or both.

CONCLUSION

Hyperechoic large kidneys, nephrocalcinosis, and renal stones are common in GSD-I. They can be present in early infancy. Abnormalities on renal sonography might suggest GSD-I in a patient with suspected inborn errors of metabolism.

Genetic Hypercalciuria

Hypercalciuria is an important, identifiable, and reversible risk factor in stone formation. The foremost and most fundamental step in dissecting the genetics of hypercalciuria is understanding its pathophysiology. Hypercalciuria is a complex trait. This article outlines the various factors that compromise the attempt to dissect the genetics of hypercalciuria, summarizes the clinical and experimental monogenic causes of hypercalciuria, and outlines the initial results from attempts in studying polygenic hypercalciuria. Finally, the problem is set in perspective of the current database, technologic advances and limitations are highlighted, and prospects of further advances in the field are speculated upon.

Bone mineral density in children, adolescents and adults with glycogen storage disease type Ia: a cross-sectional and longitudinal study

The occurrence of (symptoms related to) osteopenia is a known complication in glycogen storage disease type Ia (GSD Ia) patients. However, only limited information is available about bone mineral density (BMD). Using dual energy x-ray absorptiometry, we studied both cross-sectional and longitudinal lumbar spine areal BMD (BMD(areal) in g/cm2), areal BMD corrected for delayed bone maturation (BMD(bone age) in g/cm2), and volumetric BMD (BMD(vol) in g/cm3). Prepubertal GSD Ia patients (n = 8) had normal BMD (median z-scores BMD(areal) -0.6, BMD(bone age) -0.5 and BMD(vol) -0.5), whereas adolescent patients (n = 12) and adult patients (n = 9) had significantly reduced BMD (BMD(areal) -2.3, BMD(bone age) -1.6, BMD(vol) -2.0, and BMD(areal) -1.9, BMD(vol) -1.5, respectively). Our longitudinal study, showing a stable BMD(areal) but a trend to a decrease in BMD(vol) in prepubertal patients during follow-up, did not clarify whether the difference in BMD between prepubertal and adolescent/adult patients reflects a diminished accretion of BMD during childhood or reflects historical differences in treatment. In adolescent and adult GSD Ia patients, BMD(areal) and BMD(vol) were reduced but stable during follow-up. Especially patients with delayed bone maturation were at risk for reduced BMD. No correlation between parameters of metabolic control and BMD could be detected. Daily calcium intake was within recommended allowances ranges. Abnormal biochemical results included hypomagnesaemia (29%), hypercalciuria (34%) and reduced tubular resorption of phosphate (21%). Although the underlying pathophysiology of reduced BMD in GSD Ia remains unsolved, metabolic control should be optimized to correct as much as possible metabolic and endocrine abnormalities that may influence both bone matrix formation and bone mineral accretion.

Calcium nephrolithiasis and distal tubular acidosis in type 1 glycogen storage disease

A 36-year-old man was admitted to hospital due to right flank pain as a result of ureteral stones. He had been followed up for type 1 glycogen storage disease since the age of 11 years. He had four episodes of spontaneous stone birth during the previous 2 years, and each stone was composed mainly of calcium oxalate. Intravenous pyelography showed right hydronephrosis due to ureteral stones and bilateral multiple renal stones. We carried out transurethral ureterolithotripsy (TUL) on the right ureteral stones. The composition was a mixture of calcium oxalate and calcium phosphate. Laboratory evaluation demonstrated the association of distal renal tubular acidosis (RTA). These observations suggest that hypocitraturia and distal RTA are strongly correlated to recurrence of calcium nephrolithiasis. The patient's serum uric acid and urinary citrate excretion levels normalized after allopurinol and potassium citrate administration.

Low bone mass in glycogen storage disease type 1 is associated with reduced muscle force and poor metabolic control

OBJECTIVE

To study the relation between muscle force, bone mass, and metabolic control in patients with glycogen storage disease type (GSD 1).

STUDY DESIGN

Distal radius bone mass and density were evaluated in 19 patients with GSD 1 (15 GSD 1a, 4 GSD 1b) by means of peripheral quantitative computed tomography. Grip force was quantified with a dynamometer.

RESULTS

Height, weight, bone mass, and grip force were significantly decreased in the patients with GSD 1a, mainly as the result of low values in the poorly controlled subgroup. Boys had lower bone mass than girls. Patients with GSD 1b had higher values for bone mineral density in the trabecular compartment. In most of the study participants bone mass appeared to be adequately adapted to the mechanical requirements imposed by muscle contraction. However, 3 patients with GSD 1a had evidence for a low bone mass.

CONCLUSIONS

In GSD 1, both reduced muscle strength and a direct disease effect can contribute to low bone mass. The quality of treatment is crucial to prevent disturbances in musculoskeletal development.

Guidelines for management of glycogen storage disease type I - European Study on Glycogen Storage Disease Type I (ESGSD I)

Life-expectancy in glycogen storage disease type I (GSD I) has improved considerably. Its relative rarity implies that no metabolic centre has experience of large series of patients and experience with long-term management and follow-up at each centre is limited. There is wide variation in methods of dietary and pharmacological treatment. Based on the data of the European Study on Glycogen Storage Disease Type I, discussions within this study group, discussions with the participants of the international SHS-symposium 'Glycogen Storage Disease Type I and II: Recent Developments, Management and Outcome' (Fulda, Germany; 22-25th November 2000) and on data from the literature, guidelines are presented concerning: (1). diagnosis, prenatal diagnosis and carrier detection; (2). (biomedical) targets; (3). recommendations for dietary treatment; (4). recommendations for pharmacological treatment; (5). metabolic derangement/intercurrent infections/emergency treatment/preparation elective surgery; and (6). management of complications (directly) related to metabolic disturbances and complications which may develop with ageing and their follow-up.

CONCLUSION

In this paper guidelines for the management of GSD I are presented.

Glycogen storage disease type I: diagnosis, management, clinical course and outcome. Results of the European Study on Glycogen Storage Disease Type I (ESGSD I)

Glycogen storage disease type I (GSD I) is a relatively rare metabolic disease and therefore, no metabolic centre has experience of large numbers of patients. To document outcome, to develop guidelines about (long-term) management and follow-up, and to develop therapeutic strategies, the collaborative European Study on GSD I (ESGSD I) was initiated. This paper is a descriptive analysis of data obtained from the retrospective part of the ESGSD I. Included were 231 GSD Ia and 57 GSD Ib patients. Median age of data collection was 10.4 years (range 0.4-45.4 years) for Ia and 7.1 years (0.4-30.6 years) for Ib patients. Data on dietary treatment, pharmacological treatment, and outcome including mental development, hyperlipidaemia and its complications, hyperuricaemia and its complications, bleeding tendency, anaemia, osteopenia, hepatomegaly, liver adenomas and carcinomas, progressive renal disease, height and adult height, pubertal development and bone maturation, school type, employment, and pregnancies are presented. Data on neutropenia, neutrophil dysfunction, infections, inflammatory bowel disease, and the use of granulocyte colony-stimulating factor are presented elsewhere (Visser et al. 2000, J Pediatr 137:187-191; Visser et al. 2002, Eur J Pediatr DOI 10.1007/s00431-002-1010-0).

CONCLUSION

there is still wide variation in methods of dietary and pharmacological treatment of glycogen storage disease type I. Intensive dietary treatment will improve, but not correct completely, clinical and biochemical status and fewer patients will die as a direct consequence of acute metabolic derangement. With ageing, more and more complications will develop of which progressive renal disease and the complications related to liver adenomas are likely to be two major causes of morbidity and mortality.

Decreased urinary citrate excretion in type 1a glycogen storage disease

OBJECTIVES

To quantify urinary citrate and calcium excretion and systemic acid-base status in patients with type 1a glycogen storage disease (GSD1a) and to investigate their relationship to renal complications.

STUDY DESIGN

Fifteen patients (7 male and 8 female; age range, 3--28 years) were studied during annual evaluations of metabolic control. All were treated with intermittent doses of uncooked cornstarch. Hourly blood sampling and a 24-hour urine collection were obtained while subjects followed their usual home dietary regimen.

RESULTS

All but the youngest subject had low levels of citrate excretion (mean 2.4 +/- 1.8 mg/kg/d; 129 +/- 21 mg citrate/g creatinine). Normally, urinary citrate excretion increases with age; however, in patients with GSD1a, a strong inverse exponential relationship was found between age and citrate excretion (r = -0.84, P <.0001). Urinary citrate excretion was unrelated to markers of metabolic control. Hypercalciuria occurred in 9 of 15 patients (mean urinary calcium/creatinine ratio, 0.27 +/- 0.15) and was also inversely correlated with age (r = -0.62, P =.001).

CONCLUSIONS

Hypocitraturia that worsens with age occurs in metabolically compensated patients with GSD1a. The combination of low citrate excretion and hypercalciuria appears to be important in the pathogenesis of nephrocalcinosis and nephrolithiasis. Citrate supplementation may be beneficial in preventing or ameliorating nephrocalcinosis and the development of urinary calculi in GSD1a.

Glycogen storage diseases. Phenotypic, genetic, and biochemical characteristics, and therapy

The glycogen storage diseases are caused by inherited deficiencies of enzymes that regulate the synthesis or degradation of glycogen. In the past decade, considerable progress has been made in identifying the precise genetic abnormalities that cause the specific impairments of enzyme function. Likewise, improved understanding of the pathophysiologic derangements resulting from individual enzyme defects has led to the development of effective nutritional therapies for each of these disorders. Meticulous adherence to dietary therapy prevents hypoglycemia, ameliorates the biochemical abnormalities, decreases the size of the liver, and results in normal or nearly normal physical growth and development. Nevertheless, serious long-term complications, including nephropathy that can cause renal failure and hepatic adenomata that can become malignant, are a major concern in GSD-I. In GSD-III, the risk for hypoglycemia diminishes with age, and the liver decreases in size during puberty. Cirrhosis develops in some adult patients, and progressive myopathy and cardiomyopathy occur in patients with absent GDE activity in muscle. It remains unclear whether these complications of glycogen storage disease can be prevented by dietary therapy. Glycogen storage diseases caused by lack of phosphorylase activity are milder disorders with a good prognosis. The liver decreases in size, and biochemical abnormalities disappear by puberty.

Metabolic control and renal dysfunction in type I glycogen storage disease

This study was undertaken to determine the effect on renal function of continuous glucose therapy from early childhood. Twenty-three subjects, median age 13.9 years, range 5.9-26.9 years, with type I glycogen storage disease (GSDI) treated with continuous glucose therapy from a median age of 1.3 years, range 0.1-12.9 years, had 24 h monitoring of metabolites and glucoregulatory hormones on their home feeding regimen to assess metabolic control at approximately yearly intervals for a median duration of 8 years. During the most recent evaluation, 24 h urinary albumin excretion rate (AER), kidney size, and creatinine clearance (Ccr) were measured. CCr was unrelated to age and was increased (> 2.33 ml/s per 1.73 m2) in 10/23 (43%). Mean kidney length exceeded 2SD in 16/23 (70%). AER was normal in all five subjects < 10 years and was increased (> 10 micrograms/min) in 8/23 (35%), all > 10 years of age. AER was significantly greater in subject of similar age who started continuous glucose therapy later in childhood and was significantly higher in subjects with lower mean 24 h plasma glucose concentrations and higher mean 24 h blood lactate concentrations, both at the time of assessment of renal function and over the preceding 5 years. GSDI subjects with persistently elevated concentrations of blood lactate, serum lipids and uric acid are at increased risk of nephropathy. Optimal dietary therapy instituted early in life may delay, prevent, or slow the progression of renal disease.

The human embryonic-fetal kidney endoplasmic reticulum phosphate-pyrophosphate transport protein

Glucose-6-phosphatase is a multicomponent endoplasmic reticulum system comprising at least six different proteins, including a lumenal enzyme and several transport proteins. One of the transport proteins, T2beta, transports the substrate pyrophosphate and the product phosphate and its genetic deficiency is termed type 1c glycogen storage disease. We have used anti-T2beta antibodies for immunohistochemistry with image analysis and kinetic analysis of the glucose-6-phosphatase system to study for the temporal and spatial development of T2beta in human embryonic and fetal kidney. In metanephric kidney, there is an early predominance of T2beta expression in the ureteric bud derivatives and this changes with ontogeny such that developing nephrons, particularly proximal tubules, become dominant by mid-gestation. T2beta has the same spatial and temporal pattern as the glucose-6-phosphatase enzyme in both mesonephric and metanephric kidney. Pyrophosphate transport capacity is appropriate for the amount of glucose-6-phosphatase activity present in mid-gestation fetal kidney, in contrast to liver, where pyrophosphate transport capacity is developmentally delayed. Increasing knowledge of the temporal and spatial expression of the glucose-6-phosphatase proteins and their catalytic roles in early human development is essential for the elucidation of the aetiology of renal disease in both type I glycogen storage diseases and the developmental disorders of the glucose-6-phosphatase system.

Glomerular and tubular function in glycogen storage disease

Urinary protein and calcium excretion were assessed in 77 patients with the hepatic glycogen storage diseases (GSD): 30 with GSD-I (median age 12.4 years, range 3.2-32.9 years), 25 with GSD-III (median age 10.5 years, range 4.2-31.3 years) and 22 with GSD-IX (median age 11.8 years, range 1.2-35.4 years). Inulin (Cinulin) and para-aminohippuric acid (CPAH) clearances were also measured in 33 of these patients. Those with GSD-I had significantly greater albumin (F = 15.07, P < 0.001), retinol-binding protein (RBP) (F = 14.66, P < 0.001), N-acetyl-beta-D-glucosaminidase (NAG) (F = 9.41, P < 0.001) and calcium (F = 7.41, P = 0.001) excretion than those with GSD-III and GSD-IX. GSD-I patients (n = 18) also had significantly higher Cinulin (F = 5.57, P = 0.009), but CPAH did not differ (F = 0.77, NS). Renal function was normal in GSD-III and GSD-IX patients. In GSD-I, Cinulin (r = -0.51, P = 0.03) and NAG excretion (r = -0.40, P = 0.03) were inversely correlated with age, whereas albumin excretion was positively correlated with age (r = +0.41, P = 0.03). RBP and calcium excretion were generally high throughout all age groups. Hyperfiltration in GSD-I is associated with renal tubular proteinuria that occurs before the onset of significant albuminuria. Deficiency of glucose-6-phosphatase within the proximal renal tubule may primarily cause tubular dysfunction, glomerular hyperfiltration being a secondary phenomenon.

Bone mineralisation in type 1 glycogen storage disease

Radial bone mineral content (BMC) was measured using single photon absorptiometry in 11 prepubertal children, aged 3.4-12.6 years, with glycogen storage disease type 1 (GSD-1), 2 of whom were receiving granulocyte colony stimulating factor (G-CSF) therapy for chronic neutropenia. Patients were short (median height SD score -1.35, range -3.74 to -0.27), and had reduced BMC Z scores (median 1.79, range -6.35 to +0.27) and radial bone width Z scores (median -0.72, range -2.00 to +0.68). Those receiving G-CSF did not differ significantly from the rest of the group. Generally dietary calcium intake was low and urinary calcium excretion increased. Urinary lactate excretion was high but did not correlate with BMC Z scores. Factors regulating bone metabolism (parathyroid hormone and 25-hydroxy vitamin D concentrations) and markers of bone formation (osteocalcin and skeletal alkaline phosphatase) were not increased implying that there was no compensation for increased bone resorption.

CONCLUSION

Patients with GSD-1 may be at increased risk of fracture in later life and require close attention to metabolic control and calcium balance.

The hepatic glycogen storage diseases--problems beyond childhood

The introduction of continuous nocturnal enteral glucose feeds and uncooked cornstarch has improved the prognosis for patients with the hepatic glycogen storage diseases. An increasing number of patients are surviving into adulthood in better health, but still at some medical cost. In this review we examine bone mineralization, renal function, hepatic tumours, and vascular endothelial function in GSD I and cardiac function in GSD III. All females over the age of 5 years with GSD I, III, VI and IX had morphologically polycystic ovaries. Thirteen adult GSD I patients have been studied, and been found to have poor bone mineralization and marked renal glomerular and tubular dysfunction. More than half of these patients also had focal hepatic lesions on sonography and yet vascular endothelial function was preserved in the face of hyperlipidaemia. In 12 GSD III patients, one had a focal hepatic lesion and 6 had pronounced left ventricular hypertrophy, although cardiorespiratory function was normal. These data emphasize the multisystem nature of these disorders and highlight the need for careful longterm follow-up.

Immunohistochemical localisation of glucose-6-phosphatase in developing human kidney

The objective of our study was to determine the cellular localisation of glucose-6-phosphatase in developing human kidney using monospecific antiserum and a standard immunohistochemical method (peroxidase-antiperoxidase, PAP) on formalin fixed and paraffin embedded tissue. In embryonic and early fetal development of the metanephric kidney, glucose-6-phosphatase is located primarily in derivatives of the ureteric bud such as the pelvis, calyces and collecting ducts. In mid-fetal life as nephrons evolve and develop they become increasingly immunoreactive to glucose-6-phosphatase, such that in mature metanephric kidney the proximal tubules are highly reactive for glucose-6-phosphatase with other elements of the nephron also immunopositive albeit at lower reactivities. In addition the parietal layer of Bowman's capsule and some cells of the visceral layer are immunopositive. Only with the development of nephrons does the early predominance of glucose-6-phosphatase immunoreactivity to ureteric bud derivatives change: in mature kidney the reactivity in the collecting ducts is a small proportion of the total. In proximal tubular cells the distribution of glucose-6-phosphatase immunoreactivity is relatively uniform throughout development in contrast to collecting ducts where in fetal life this reactivity is displaced to the apices and basal areas by intracellular glycogen deposits. The mesonephric kidney has a similar pattern of glucose-6-phosphatase immunoreactivity to that of metanephric kidney. The availability of monospecific antiserum to glucose-6-phosphatase and immunohistochemical methods now allows an alternative approach to cellular localisation. Many of the difficulties in the fixation of tissue and assay of glucose-6-phosphatase activity inherent in conventional histochemical methods are avoided by such methods.