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

Assessment of the diagnosis, treatment, and follow-up of a group of Turkish pediatric glycogen storage disease type 1b patients with varying clinical presentations and a novel mutation

OBJECTIVES

Glycogen storage disease (GSD) type 1b is a multisystemic disease in which immune and infectious complications are present, different from GSD type 1a. Treatment with granulocyte-colony stimulating factor (G-CSF) is often required in the management of neutropenia and inflammatory bowel disease. Recently, an alternative treatment option to G-CSF has been preferred, like empagliflozin. To report on the demographics, genotype, clinical presentation, management, and complications of pediatric patients with glycogen storage disease type 1b (GSD 1b).

METHODS

A retrospective analysis of the clinical course of eight patients with GSD type 1b whose diagnosis was confirmed by molecular testing.

RESULTS

The mean age at referral was four months. The diagnosis of GSD 1b was based on clinical and laboratory findings and supported by genetic studies. One patient presented with an atypical clinical finding in the form of hydrocephalus at the time of first admission. The first symptom was abscess formation on the scalp due to neutropenia in another patient. Other patients had hypoglycemia at the time of admission. All patients presented suffered from neutropenia, which was managed with G-CSF, except one. Hospitalizations for infections were frequent. One patient developed chronic diarrhea and severe infections, which have been brought under control with empagliflozin.

CONCLUSIONS

Neutropenia is an essential finding in GSD 1b and responsible for complications. The coexistence of hypoglycemia and neutropenia should bring to mind GSD 1b. Empagliflozin can be a treatment option for neutropenia, which is resistant to G-CSF treatment.

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.

Renal pyramids: focused sonography of normal and pathologic processes

In neonates and children, sonographic examinations of the renal pyramids may depict a spectrum of unique changes in echogenicity due to the effects of physiologic processes or a wide variety of pathologic processes that may affect the collecting ducts or interstitium of the pyramids. Focused sonographic evaluation of the pyramids with high-frequency transducers produces the most detailed images of the pyramids, revealing some appearances not previously reported, to the authors' knowledge. The authors highlight the clinical settings in which they have documented detailed changes in the echogenicity of the pyramids. The patterns of altered echogenicity alone may reflect a specific cause but in many instances are nonspecific, with clinical and biochemical correlation required to establish a more precise diagnosis. However, there is a lack of histologic data to completely explain the mechanism of many of these changes in echogenicity in all of the processes. As the authors have expanded their use of the focused sonographic technique, they have been able to depict altered echogenicity in the pyramids in greater numbers of children in whom an explanation for the changes is not always immediately apparent; for now, the cause must be considered idiopathic. More work is required to expand the use of this focused technique together with clinical, biochemical, and histologic correlation in an attempt to offer more complete explanations for the changes in echogenicity of the pyramids.

Early diagnosis and treatment may prevent the development of complications in an adult patient with glycogen storage disease type Ia

Type Iota(a) glycogen storage disease (GSD Iota(a)) is caused by the deficiency of glucose-6-phosphatase activity, which results in metabolic disorder and organ failure, including renal failure. GSD Iota(a) patients are generally diagnosed at a median age of 6 months. However, we report a 20-year-old Japanese female with newly diagnosed GSD Iota(a) . The renal disorder of GSD Iota(a) is considered to be produced by glomerular hyperfiltration, TGF-beta expression which is induced by renin-angiotensin-aldosterone system (RAS) and uric acid, and the increase in both small dense LDL and modified LDL which is characteristic of GSD Iota(a) as well as hypertriglyceridemia. With the administration of intensive therapies, including angiotensin type 1-receptor blocker and some lipid lowering drugs, along with traditional dietary therapy, daily proteinuria of the patient improved from 2.1 g to 0.78 g. Although the patients of GSD Iota(a) should receive an early and accurate diagnosis and effective therapies before the age of 1 year, the combination of traditional dietary therapies and intensive therapies may have therapeutic potential for the complications of adult patients. In this report, we describe the management of renal disease and the characteristic features of this metabolic disorder.

Congenital type IV glycogenosis: the spectrum of pleomorphic polyglucosan bodies in muscle, nerve, and spinal cord with two novel mutations in the GBE1 gene

A diagnosis of GSD-IV was established in three premature, floppy infants based on characteristic, however unusually pleomorphic polyglucosan bodies at the electron microscopic level, glycogen branching enzyme deficiency in two cases, and the identification of GBE1 mutations in two cases. Pleomorphic polyglucosan bodies in muscle fibers and macrophages, and less severe in Schwann cells and microglial cells were noted. Most of the inclusions were granular and membrane-bound; others had an irregular contour, were more electron dense and were not membrane bound, or homogenous ('hyaline'). A paracrystalline pattern of granules was repeatedly noted showing a periodicity of about 10 nm with an angle of about 60 degrees or 120 degrees at sites of changing linear orientation. Malteser crosses were noted under polarized light in the larger inclusions. Some inclusions were PAS positive and others were not. Severely atrophic muscle fibers without inclusions, but with depletion of myofibrils in the plane of section studied indicated the devastating myopathic nature of the disease. Schwann cells and peripheral axons were less severely affected as was the spinal cord. Two novel protein-truncating mutations (c.1077insT, p.V359fsX16; g.101517_127067del25550insCAGTACTAA, DelExon4-7) were identified in these families. The present findings extend previous studies indicating that truncating GBE1 mutations cause a spectrum of severe diseases ranging from generalized intrauterine hydrops to fatal perinatal hypotonia and fatal cardiomyopathy in the first months of life.

Metabolic characterisation of plasma in juveniles with glycogen storage disease type 1a (GSD1a) by high-resolution (1)H NMR spectroscopy

This paper reports the first application of high-resolution (1)H NMR spectroscopy to the plasma of five juveniles with glycogen storage disease type 1a (GSD1a), permitting the characterisation of the plasma metabolic profile and the identification of alterations relative to a set of control samples. The relaxation-weighted spectra allowed changes in low molecular weight compounds to be detected more clearly, whereas diffusion-edited spectra were used to characterise the plasma lipoprotein profile. Low molecular weight metabolites with altered levels in most patients were lactate, ketone bodies, acetate, creatine/creatinine and glucose. One of the patients showed distinctively lower glucose levels and higher lactate and ketone body contents, suggesting poorer metabolic control of the disease compared with other patients. In addition, a metabolite tentatively identified as alpha-hydroxyisobutyrate was only detected in the spectra of GSD1a plasmas, representing, therefore, a possible novel GSD1a biomarker. Total lipoprotein contents were higher in the plasma from GSD1a patients. Furthermore, lower HDL and higher VLDL + LDL levels also characterised the plasma of these patients. Preliminary results on principal component analysis of (1)H NMR spectra allowed a clear separation between GSD1a and control plasmas. The specificity of the changes observed to GSD1a is discussed, together with the recognised potential of NMR and pattern recognition methods for aiding the diagnosis of GSD1a.

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.