Glycogen storage disease type VI
Encyclopedia
Glycogen storage disease type VI (GSD VI) is a type of glycogen storage disease
caused by a deficiency in liver glycogen phosphorylase or other components of the associated phosphorylase cascade system.
It is also known as "Hers' disease", after Henri G. Hers
, who characterized it in 1959.
The scope of GSD VI now also includes glycogen storage disease type VIII, IX (caused by phosphorylase b kinase deficiency) and X (deficiency of protein kinase A). These were previously considered to be distinct GSD types.
The incidence of GSD VI is approximately 1 case per 65,000-85,000 births, representing approximately 30% all cases of glycogen storage disease
. Approximately 75% of these GSD VI cases result from the X-linked recessive
forms of phosphorylase kinase deficiency. All other forms are autosomal recessive.
and growth retardation early in childhood. Mild hypoglycemia
, hyperlipidemia
, and hyperketosis may occur. Lactic acid
and uric acid
levels are normal.
Glycogen storage disease
Glycogen storage disease is the result of defects in the processing of glycogen synthesis or breakdown within muscles, liver, and other cell types. GSD has two classes of cause: genetic and acquired. Genetic GSD is caused by any inborn error of metabolism involved in these processes...
caused by a deficiency in liver glycogen phosphorylase or other components of the associated phosphorylase cascade system.
It is also known as "Hers' disease", after Henri G. Hers
Henri G. Hers
Henri-Géry Hers is a Belgian physiologist and biochemist, and was a professor at the Universite Catholique de Louvain. Hers' suffers from an inborn glycogen metabolism disorder caused by deficiency of hepatic phosphorylase associated with an enlarged liver and mild hypoglycaemia...
, who characterized it in 1959.
The scope of GSD VI now also includes glycogen storage disease type VIII, IX (caused by phosphorylase b kinase deficiency) and X (deficiency of protein kinase A). These were previously considered to be distinct GSD types.
The incidence of GSD VI is approximately 1 case per 65,000-85,000 births, representing approximately 30% all cases of glycogen storage disease
Glycogen storage disease
Glycogen storage disease is the result of defects in the processing of glycogen synthesis or breakdown within muscles, liver, and other cell types. GSD has two classes of cause: genetic and acquired. Genetic GSD is caused by any inborn error of metabolism involved in these processes...
. Approximately 75% of these GSD VI cases result from the X-linked recessive
X-linked recessive
X-linked recessive inheritance is a mode of inheritance in which a mutation in a gene on the X chromosome causes the phenotype to be expressed in males and in females who are homozygous for the gene mutation X-linked recessive inheritance is a mode of inheritance in which a mutation in a gene on...
forms of phosphorylase kinase deficiency. All other forms are autosomal recessive.
Presentation
Patients generally have a benign course, and typically present with hepatomegalyHepatomegaly
Hepatomegaly is the condition of having an enlarged liver. It is a nonspecific medical sign having many causes, which can broadly be broken down into infection, direct toxicity, hepatic tumours, or metabolic disorder. Often, hepatomegaly will present as an abdominal mass...
and growth retardation early in childhood. Mild hypoglycemia
Hypoglycemia
Hypoglycemia or hypoglycæmia is the medical term for a state produced by a lower than normal level of blood glucose. The term literally means "under-sweet blood"...
, hyperlipidemia
Hyperlipidemia
Hyperlipidemia, hyperlipoproteinemia, or hyperlipidaemia is the condition of abnormally elevated levels of any or all lipids and/or lipoproteins in the blood...
, and hyperketosis may occur. Lactic acid
Lactic acid
Lactic acid, also known as milk acid, is a chemical compound that plays a role in various biochemical processes and was first isolated in 1780 by the Swedish chemist Carl Wilhelm Scheele. Lactic acid is a carboxylic acid with the chemical formula C3H6O3...
and uric acid
Uric acid
Uric acid is a heterocyclic compound of carbon, nitrogen, oxygen, and hydrogen with the formula C5H4N4O3. It forms ions and salts known as urates and acid urates such as ammonium acid urate. Uric acid is created when the body breaks down purine nucleotides. High blood concentrations of uric acid...
levels are normal.