2. • Glycogen is the form in which the sugar glucose is
stored in muscle and liver as a polymer, acting as a
reserve energy source.
• In the GSDs glycogen accumulates in excessive
amounts in skeletal muscle, cardiac muscle, and/or
liver because of a variety of inborn errors of the
enzymes involved in synthesis and degradation of
glycogen.
• In addition, because of the metabolic block,
glycogen is unavailable as a normal glucose
source.
• This can result in hypoglycemia, impairment of liver
function and neurological abnormalities.
3. Some Types of GSD and the parts of the body they affect the most
include:
Type 0 (Lewis' disease) – Liver.
Type I (von Gierke’s disease) Type Ia – Liver, kidneys, intestines; Type
Ib – Liver, kidneys, intestines, blood cells.
Type II (Pompe’s disease) – Muscles, heart, liver, nervous system,
blood vessels.
Type III (Forbes-Cori disease) – Liver, heart, skeletal muscles, blood
cells.
Type IV (Andersen’s disease) – Liver, brain, heart, muscles, skin,
nervous system.
Type V (McArdle’s disease) – Skeletal muscles.
Type VI (Hers’ disease) – Liver, blood cells.
Type VII (Tarui’s disease) – Skeletal muscles, blood cells.
Type IX – Liver.
Type XI (Fanconi-Bickel syndrome) – Liver, kidneys, intestines
GSDs
4. In all, there are now around 30 different GSD
entities identified but we briefly describe six
of the major types.
For each, there is a specific enzyme defect
involving one of the steps in glycogen
synthesis or degradation.
Although listed by their numerical place in
the classification, types II (Pompe) and V
(McArdle) primarily affect muscle whilst the
others primarily affect the liver.
Among the rare types are Fanconi-Bickel
syndrome (GSD type XI) and Aldolase A
deficiency.
5. Infants with Pompe disease usually present in the
first few months of life with floppiness (hypotonia)
and delay in the gross motor milestones because of
muscle weakness.
They then develop an enlarged heart and die from
cardiac failure in the first or second year.
Voluntary and cardiac muscle accumulates glycogen
because of a deficiency of the lysosomal enzyme α-
1,4-glucosidase, which is needed to break down
glycogen.
The diagnosis can be confirmed by enzyme assay of
white blood cells or fibroblasts.
Early reports of enzyme replacement therapy appear
promising.
Pompe Disease (GSD II)
