Glycogen storage diseases (GSDs) are metabolic disorders of glycogen metabolism. In aggregate, GSDs are not considered rare diseases, but every individual type are. The overall estimated GSD incidence is 1 case per 20,000-43,000 live births, and a prevalence of 1:100,000 is considered for main types (including I, II, II, V and IX). There are 19 types which are classified by enzyme deficiency and affected tissue. Most of them are inherited in an autosomal recessive manner, except for one X-linked GSDIX and Danon subtypes. Disorders related with creation, deposits and degradation of glycogen, may primarily affect the liver (hepatic GSDs), the muscles (muscle GSDs), or in a multiorganic manner (mainly Pompe). The common characteristic of all types of GSDs is the alteration of some step in glycogenolysis/glycolysis pathway, as can be seen in figures 1a and 1b.
Glycogen storage diseases (GSDs) are metabolic disorders of glycogen metabolism. In aggregate, GSDs are not considered rare diseases, but every individual type are. The overall estimated GSD incidence is 1 case per 20,000-43,000 live births [1], and a prevalence of 1:100,000 is considered for main types (including I, II, II, V and IX). There are 19 types which are classified by enzyme deficiency and affected tissue. Most of them are inherited in an autosomal recessive manner, except for one X-linked GSDIX and Danon subtypes. Disorders related with creation, deposits and degradation of glycogen, may primarily affect the liver (hepatic GSDs), the muscles (muscle GSDs), or in a multiorganic manner (mainly Pompe) [2]. The common characteristic of all types of GSDs is the alteration of some step in glycogenolysis/glycolysis pathway, as can be seen in figures 1a and 1b.
Figure 1. (a) Glycolysis–gluconeogenesis pathway showing steps disrupted in every GSD. Abbreviations: Glycogen Synthase Deficiency (GSD 0); Von Gierke Disease (GSD Ia, Ib, Ic, Id); Pompe disease (GSD II); Cori-Forbes Disease (GSD III); Andersen Disease (GSD IV); McArdle Disease (GSD V); Hers Disease (GSD VI); Phosphofructokinase Deficiency (GSD VII); Muscle Phosphorylase b Kinase Deficiency (GSD VIII); Liver Phosphorylase Kinase Deficiency (GSD IX); Fanconi-Bickel Syndrome (GSD XI); Phosphoglucomutase 1 Deficiency (GSD XIV); Glycogenin Deficiency (XV). (b) “Zoomed in” detail of pyruvate formation in final glycolysis steps from Figure 1a. Abbreviations: Muscle Phosphoglycerate Mutase Deficiency (GSDX); Aldolase A Deficiency (GSDXII); Enolase 3 Deficiency (GSDXIII).
An overall clinical summary of GSDs are in table 1.
Table 1. Main gene and clinical characteristics of GSDs types. Abbreviations: G6PC1 (glucose-6-phosphatase catalytic subunit), SLC37A4 (Solute Carrier Family 37 Member 4), GAA (acid alpha-glucosidase), AGL (amylo-alpha-1,6-glucosidase), PYGM (glycogen phosphorylase, muscle form), PYGL (glycogen phosphorylase, liver form), PHKA1 (phosphorylase kinase regulatory subunit alpha 1), PHKA2 (phosphorylase kinase regulatory subunit alpha 2), PHKB (phosphorylase kinase regulatory subunit beta), PHKG2 (phosphorylase kinase regulatory subunit gamma 2), GYS1 (glycogen synthase 1), GYS2 (glycogen synthase 2), LAMP2 (lysosomal-associated membrane protein 2), GBE1 (1,4-alpha-glucan-branching enzyme), PFKM (phosphofructokinase, muscle), PGAM2 (phosphoglycerate mutase 2), SLC2A2 (solute carrier family 2 member 2), ALDOA (aldolase A), ENO3 (beta-enolase), PGM1 (phosphoglucomutase 1), GYG1 (glycogenin 1), EPM2A (Glucan Phosphatase, Laforin), NHLRC1 (NHL Repeat Containing E3 Ubiquitin Protein Ligase 1)
GSD TYPE |
ORGAN INVOLVEMENT |
VARIANT |
MUTATED GENE |
MAIN FINDINGS |
0 (glycogen synthase deficiency) [10] |
Liver |
a |
GYS2 |
Fasting ketotic hypoglycemia, short stature, osteopenia |
Skeletal muscle |
b [11] |
GYS1 |
Exercise intolerance, epilepsy, long QT syndrome, recurrent attacks of exertional syncope, muscle weakness, cardiac arrest |
|
I (Von Gierke Disease) [3] |
Liver |
a |
G6PC1 |
Severe hypoglycaemia, hepatomegaly, lactic acidosis, hyperuricemia, hyperlipidaemia, hypertriglyceridemia, hypoglycaemic seizures, bleeding, epistaxis |
b |
SLC37A4 |
Same as “a” variant plus impaired neutrophil and monocyte function, chronic neutropenia, recurrent bacterial infections, oral and intestinal mucosal ulcers |
||
II (Pompe Disease) [4] |
Multiorganic |
Infantile-onset Pompe disease (IOPD) |
GAA |
Hypotonia, generalized muscle weakness, hypertrophic cardiomyopathy |
Late-onset Pompe disease (LOPD) |
Proximal muscle weakness, respiratory insufficiency |
|||
II (Danon Disease, X-linked) [12] |
b |
LAMP2 |
Hypertrophic cardiomyopathy, cardiac conduction abnormalities, weakness, retinopathy |
|
III (Cori-Forbes disease) [5] |
Liver and muscle |
a |
AGL |
Ketotic hypoglycemia, hepatomegaly, hyperlipidemia, elevated hepatic transaminases, hypertrophic cardiomyopathy, skeletal myopathy, weakness |
Liver |
b |
Ketotic hypoglycemia, hepatomegaly, hyperlipidemia, elevated hepatic transaminases |
||
IV (Andersen disease) [13] |
Skeletal muscle |
fatal perinatal neuromuscular |
GBE1 |
Fetal akinesia deformation sequence, polyhydramnios, fetal hydrops, arthrogryposis, severe hypotonia, muscle atrophy at birth |
congenital neuromuscular |
Hypotonia at birth, respiratory distress, dilated cardiomyopathy |
|||
Liver |
classic (progressive) |
Hepatomegaly, liver dysfunction, progressive liver cirrhosis, hypotonia, cardiomyopathy |
||
non-progressive |
Hepatomegaly, liver dysfunction, myopathy, hypotonia |
|||
Skeletal muscle |
childhood neuromuscular |
Chronic and progressive myopathy, dilated cardiomyopathy |
||
Adult Polyglucosan Body Disease [14] |
- |
- |
Progressive neurogenic bladder, spasticity, weakness, sensory loss in extremities, autonomic dysfunction, mild cognitive difficulties |
|
V (McArdle disease) [6,7] |
- |
- |
PYGM |
Fatigue, myalgia, muscle cramps, “second wind” phenomenon |
VI (Hers disease) [15] |
Liver |
- |
PYGL |
Hepatomegaly, poor growth, ketotic hypoglycemia, elevated hepatic transaminases, hyperlipidemia, low prealbumin level short stature, delayed puberty, osteopenia, osteoporosis (symptoms improve with age) |
VII (phosphofructokinase deficiency) [16] |
Skeletal muscle |
- |
PFKM |
Exercise intolerance, myalgias, cramps, episodic myoglobinuria, hemolytic anaemia, hyperuricemia |
VIII (phosphorylase b kinase deficiency, X-linked) [8] |
- |
- |
PHKA1 |
Exercise intolerance, myalgia, muscular cramps, myoglobinuria, weakness |
IX (phosphorylase b kinase deficiency, X-linked) [8,9] |
Liver |
- |
PHKA2 |
hepatomegaly, growth retardation, fasting ketosis, hypoglycaemia (symptoms improve with age) |
IX (phosphorylase b kinase deficiency) |
Liver and skeletal muscle |
- |
PHKB |
Sum of symptoms for type VIII and IX |
Liver |
- |
PHKG2 |
Hepatomegaly, growth retardation, fasting ketosis, hypoglycaemia (symptoms improve with age) |
|
X (phosphoglycerate mutase deficiency) [17] |
Skeletal muscle |
- |
PGAM2 |
Myalgia, cramps, muscle necrosis, myoglobinuria |
XI (Fanconi-Bickel syndrome) [18] |
Liver |
- |
SLC2A2 |
Hepatomegaly, fasting hypoglycemia, tubular nephropathy, severely stunted growth |
XII (aldolase A deficiency) [19] |
Skeletal muscle |
- |
ALDOA |
Non-spherocytic hemolytic anemia, mental retardation, rhabdomyolysis |
XIII (beta-enolase deficiency) [20] |
Skeletal muscle |
- |
ENO3 |
Exercise intolerance, myalgia, recurrent rhabdomyolysis |
XIV (phosphoglucomutase 1 deficiency) [21] |
Multiorganic |
- |
PGM1 |
Hepatopathy, bifid uvula, malignant hyperthermia, hypogonadotropic hypogonadism, growth retardation, hypoglycemia, myopathy, dilated cardiomyopathy, cardiac arrest |
XV (glycogenin 1 deficiency) [22] |
Skeletal muscle |
- |
GYG1 |
Progressive, widespread muscle weakness, wasting, cardiac involvement in some cases |
This entry is adapted from the peer-reviewed paper 10.3390/ijms22094381