Assignment On Glycogen Storage Disease.

Title: Glycogen Storage Disease
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GSD in children is a rare condition which changes the manner in which the body makes
use of glycogen stored in the form of glucose or sugar. As glycogen is the main energy
source for our body, it is stored in the
liver [5]. When the body requires
more energy than certain protein
enzymes break down glycogen into
glucose and releases it out in the
body. A child with GSD misses out
on one of the enzymes which breaks
glycogen down. When such enzymes
are missing, one of the enzymes
which breaks glycogen goes missing.
In case of missing glycogen then it
can build up in the liver or glycogen
might not be formed properly [9].
GSD is generally hereditary and
passed from parents to children. This
condition has been often seen in
babies or young children.
o Causes and type of GSD:
GSD is generally known to pass down from parents to children and hence is regarded
to be hereditary in nature. It happens due to the presence of abnormal genes in parents
or due to gene mutation which impacts in a specific manner by which glycogen is
stored or used [6]. In most cases GSD occurs due to the same abnormal genes being
passed down from parents to their children and most parents does not show any
symptom of the disease.
GSD is grouped by the type of enzyme which goes missing. Every distinct type of
GSD has their own specific needs and symptoms, requiring varied treatment [8]. GSD
can be of varied types, some of the common types occurring in children are I, III, IV
and VI.
Type I
Type I is also referred to as von Gierke disease. It is one of the most common type of
GSD. In this type of GSD, children do not possess the enzyme to break glycogen into
glucose, leading to glycogen build up in the liver [2]. Its symptoms can appear in 3 to
4 months old and may lead to low blood sugar (hypoglycemia) leading to swollen
belly from enlarged liver. It is hereditary in nature.
Type III
In type III GSD, which is also known as Cori disease or Forbes disease, children lack
debranching enzyme that breaks down glycogen. This collects in muscle and liver
tissue. Symptoms need include swollen belly, weak muscles and delayed growth. It is
caused by deficiency of the enzyme amylo-1, 6 glucosidase or debrancher enzyme. It
is also due to AGL gene mutation.
Type IV
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In type IV GSD also referred to as Anderson disease, children develop abnormal
glycogen. This triggers body’s infection-fighting system creating scarring of the liver,
muscles and the heart. It is caused due to mutation in the GBE1 gene. This gene
normally carries instruction for making glycogen branching enzyme.
Type VI
It is caused due to storage disease caused by deficiency in liver glycogen
phosphorylase and other components associated with phosphorylase cascade system.
This is also referred to as “Hers’ disease”
o Normal liver function
Normal liver function is to
filter out blood coming
from the digestive tract
before it passes on to the
rest of the body. The liver
is also responsible for
detoxification of chemicals
and metabolizing drugs. It
secrets bile that ends up in
the intestine. The liver also
makes crucial proteins that
is important for clotting of
the blood and other
functions [3]. In normal
situation, the liver serves as
a store for glucose to be
used throughout the body, especially for the central nervous system. The human body
is said to consume approximately 60% of the blood glucose in fasting, in sedentary
individuals. Thus, the liver storing glycogen, act as a reservoir for energy for normal
human body [7].
o Liver function changes caused by GSD:
The body’s cells requires a steady supply of fuel/ energy for conducting various
functions, which comes from sugar in the body by breaking down of glucose. Glucose
in turn comes from the various food that we eat [10]. Our body uses as much glucose
from the food eaten and stores the rest in the liver for later usage. Prior to being stored
in the liver, the body combines simple glucose units into new and complex sugars
called glycogen. Glycogen is stored in the liver and muscle cells. When the body
requires extra fuel, then it triggers a mechanism to turn back glucose stored in the
liver to form glycogen. Presence of special protein in the liver referred to as enzymes
breaks down glycogen. When a child is born with the enzyme being missing for this
process then it might not work right.
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