Glycogen storage disease type III with hypoketosis

Metabolic Cardiomyopathies and Cardiac Defects in Inherited Disorders of Carbohydrate Metabolism: A Systematic Review

Heart failure (HF) is a progressive chronic disease that remains a primary cause of death worldwide, affecting over 64 million patients. HF can be caused by cardiomyopathies and congenital cardiac defects with monogenic etiology. The number of genes and monogenic disorders linked to development of cardiac defects is constantly growing and includes inherited metabolic disorders (IMDs). Several IMDs affecting various metabolic pathways have been reported presenting cardiomyopathies and cardiac defects. Considering the pivotal role of sugar metabolism in cardiac tissue, including energy production, nucleic acid synthesis and glycosylation, it is not surprising that an increasing number of IMDs linked to carbohydrate metabolism are described with cardiac manifestations. In this systematic review, we offer a comprehensive overview of IMDs linked to carbohydrate metabolism presenting that present with cardiomyopathies, arrhythmogenic disorders and/or structural cardiac defects. We identified 58 IMDs presenting with cardiac complications: 3 defects of sugar/sugar-linked transporters (GLUT3, GLUT10, THTR1); 2 disorders of the pentose phosphate pathway (G6PDH, TALDO); 9 diseases of glycogen metabolism (GAA, GBE1, GDE, GYG1, GYS1, LAMP2, RBCK1, PRKAG2, G6PT1); 29 congenital disorders of glycosylation (ALG3, ALG6, ALG9, ALG12, ATP6V1A, ATP6V1E1, B3GALTL, B3GAT3, COG1, COG7, DOLK, DPM3, FKRP, FKTN, GMPPB, MPDU1, NPL, PGM1, PIGA, PIGL, PIGN, PIGO, PIGT, PIGV, PMM2, POMT1, POMT2, SRD5A3, XYLT2); 15 carbohydrate-linked lysosomal storage diseases (CTSA, GBA1, GLA, GLB1, HEXB, IDUA, IDS, SGSH, NAGLU, HGSNAT, GNS, GALNS, ARSB, GUSB, ARSK). With this systematic review we aim to raise awareness about the cardiac presentations in carbohydrate-linked IMDs and draw attention to carbohydrate-linked pathogenic mechanisms that may underlie cardiac complications.

Normoglycemic Ketonemia as Biochemical Presentation in Ketotic Glycogen Storage Disease

BACKGROUND

According to the textbooks, the ketotic glycogen storage disease (GSD) types 0, III, VI, IX, and XI are associated with fasting ketotic hypoglycemia and considered milder as gluconeogenesis is intact.

METHODS

A retrospective cohort study of biochemical profiles from supervised clinical fasting studies is performed in ketotic GSD patients in our metabolic center. For data analysis, hypoglycemia was defined as plasma glucose concentration <2.6 mmol/L. Total KB was defined as the sum of blood acetoacetate and β-hydroxybutyrate concentrations. If the product of glucose and KB concentrations was greater than 10, a ketolysis defect was suspected.

RESULTS

Data could be collected from 13 fasting studies in 12 patients with GSD III (n = 4), GSD VI (n = 3), and GSD IX (n = 5). Six patients remained normoglycemic with median glucose concentration of 3.9 mmol/L (range, 2.8-4.6 mmol/L) and median total KB concentration of 1.9 mmol/L (range, 0.6-5.1 mmol/L). The normoglycemic patients included type VI (3 out of 3) and type IX (3 out of 5) patients. All type III patients developed ketotic hypoglycemia. Interestingly, in five patients (one GSD III, one GSD VI, and three GSD IX), the biochemical profile suggested a ketolysis defect.

CONCLUSION

Normoglycemic ketonemia is a common biochemical presentation in patients with GSD types VI and IX, and ketonemia can precede hypoglycemia in all studied GSD types. Therefore, GSD VI and GSD IX should be added to the differential diagnosis of ketotic normoglycemia, and KB concentrations should be routinely measured in ketotic GSD patients.