Prenatal diagnosis and carrier detection for glycogen storage disease type III using polymorphic DNA markers

Glycogen storage disease type III-hepatocellular carcinoma a long-term complication?

BACKGROUND/AIMS

Glycogen storage disease III (GSD III) is caused by a deficiency of glycogen-debranching enzyme which causes an incomplete glycogenolysis resulting in glycogen accumulation with abnormal structure (short outer chains resembling limit dextrin) in liver and muscle. Hepatic involvement is considered mild, self-limiting and improves with age. With increased survival, a few cases of liver cirrhosis and hepatocellular carcinoma (HCC) have been reported.

METHODS

A systematic review of 45 cases of GSD III at our center (20 months to 67 years of age) was reviewed for HCC, 2 patients were identified. A literature review of HCC in GSD III was performed and findings compared to our patients.

CONCLUSIONS

GSD III patients are at risk for developing HCC. Cirrhosis was present in all cases and appears to be responsible for HCC transformation There are no reliable biomarkers to monitor for HCC in GSD III. Systematic evaluation of liver disease needs be continued in all patients, despite lack of symptoms. Development of guidelines to allow for systematic review and microarray studies are needed to better delineate the etiology of the hepatocellular carcinoma in patients with GSD III.

DNA-based subtyping of glycogen storage disease type III: mutation and haplotype analysis of the AGL gene in Chinese

Glycogen storage disease type III (GSD III) is an inborn error of glycogen metabolism caused by a deficiency of glycogen debranching enzyme (AGL). Here, we investigate two unrelated Hong Kong Chinese GSD III patients and identify a novel 5-base pair deletional mutation, 2715_2719delTCAGAin exon 22, in one patient and a nonsense mutation, 1222C>T (R408X) in exon 11, in another patient. Since GSD IIIb is only caused by mutation in exon 3 of the AGL gene, we diagnose our patients to have GSD IIIa, which is consistent with the clinical diagnosis. Until now, R408X has only been reported in Faroe Islands GSDIII patients and was thought to demonstrate a founder effect. In this study, haplotyping of the disease-bearing chromosomes in the AGL locus by 19 intragenic single nucleotide polymorphisms shows that R408X is linked with IVS16+8T and IVS23-21T in our patient while R408X is linked with IVS16+8C and IVS23-21A in the Faroe Islands. The different haplotypes of R408X in Chinese and Faroese indicated that R408X is a recurrent mutation.

Metabolic myopathies: a clinical approach; part II

Major recent advances in the field of metabolic myopathies have helped delineate the genetic and biochemical basis of these disorders. This progress has also resulted in the development of new diagnostic and therapeutic methodologies. In this second part, we present an updated review of the main nonlysosomal and lysosomal glycogenoses and lipid metabolism defects that manifest with signs of transient or permanent muscle dysfunction. Our intent is to increase the pediatric neurologist's familiarity with these conditions and thus improve decision making in the areas of diagnosis and treatment.

Acid maltase deficiency and related myopathies

There are 11 glycogen diseases (GSD), nine of which are associated with myopathy. Most of these glycogen storage myopathies are associated with dynamic symptoms and signs in that the major neuromuscular complaints are exercise-induced muscle pain, cramps, and myoglobinura (e.g., GSD V or McArdle's disease associated with myophosphorylase deficiency). The other types of glycogen storage myopathies are considered static in that they are associated with fixed weakness rather than dynamic symptoms and signs. The static glycogen storage myopathies include: GSD I or Pompe's disease (acid maltase or (-glucosidase deficiency), GSD II or Cori-Forbes disease (debranching enzyme deficiency), and GSD IV or Andersen's disease (branching enzyme deficiency). This article reviews the clinical, laboratory, electrophysiologic, histopathologic, and pathogenesis of these static GSD myopathies.

The molecular diagnosis of metabolic myopathies

The metabolic myopathies are distinguished by extensive clinical and genetic heterogeneity within and between individual disorders. There are a number of explanations for the variability observed that go beyond single gene mutations or degrees of heteroplasmy in the case of mitochondrial DNA mutations. Some of the contributing factors include protein subunit interactions, tissue-specificity, modifying genetic factors, and environmental triggers. Advances in the molecular analysis of metabolic myopathies during the last decade have not only improved the diagnosis of individual disorders but also helped to characterize the contributing factors that make these disorders so complex.

The molecular background of glycogen metabolism disorders

The molecular pathology of classical glycogen storage disorders, glycogen synthase deficiency and Fanconi-Bickel syndrome is reviewed. The isolation of the respective cDNAs, the chromosomal localization of the genes and the elucidation of the genomic organization enabled mutation analysis in most disorders. The findings have shed light on the multi-protein structure of the glucose-6-phosphatase system, the phosphorylase kinase enzymatic complex and the molecular background of the differential tissue expression in debranching enzyme deficiency. The immediate practical benefit of these studies is our extending ability to predict the outcome of clinical variants and to offer genetic counseling to most families. The elucidation of the tertiary structure of these proteins and their structure-function relationship poses major challenges for the future.