Glycogen storage disease
A glycogen storage disease (GSD, also glycogenosis and dextrinosis) is a metabolic disorder caused by an enzyme deficiency affecting glycogen synthesis, glycogen breakdown, or glucose breakdown, typically in muscles and/or liver cells.GSD has two classes of cause: genetic and acquired. Genetic GSD is caused by any inborn error of metabolism (genetically defective enzymes) involved in these processes.  In livestock, acquired GSD is caused by intoxication with the alkaloid castanospermine.

Types
Remarks:

Some GSDs have different forms, e.g. infantile, juvenile, adult (late-onset).
Some GSDs have different subtypes, e.g. GSD1a / GSD1b, GSD9A1 / GSD9A2 / GSD9B / GSD9C / GSD9D.
GSD type 0: Although glycogen synthase deficiency does not result in storage of extra glycogen in the liver, it is often classified with the GSDs as type 0 because it is another defect of glycogen storage and can cause similar problems.
GSD type VIII (GSD 8): In the past it was considered a distinct condition, however it is now classified with GSD type VI or GSD IXa1; it has been described as X-linked recessive inherited.
GSD type XI (GSD 11): Fanconi-Bickel syndrome, hepatorenal glycogenosis with renal Fanconi syndrome, no longer considered a glycogen storage disease.
GSD type XIV (GSD 14): Now classed as Congenital disorder of glycosylation type 1 (CDG1T), affects the phosphoglucomutase enzyme (gene PGM1).
Lafora disease is considered a complex neurodegenerative disease and also a glycogen metabolism disorder.

Diagnosis
Treatment
Treatment is dependent on the type of glycogen storage disease. GSD I is typically treated with frequent small meals of carbohydrates and cornstarch, called modified cornstarch therapy, to prevent low blood sugar, while other treatments may include allopurinol and human granulocyte colony stimulating factor.

Epidemiology
Overall, according to a study in British Columbia, approximately 2.3 children per 100,000 births (1 in 43,000) have some form of glycogen storage disease. In the United States, they are estimated to occur in 1 per 20,000–25,000 births. Dutch incidence rate is estimated to be 1 per 40,000 births.
While a Mexican incidence showed 6.78:1000 male newborns.

References


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