GSD type I is split into two main sub-types – Ia and Ib. In both sub-types your liver glycogen stores cannot release glucose into the blood stream.
In type Ia, an enzyme called glucose-6-phosphatase does not work properly. This means that the liver cannot change a substance called glucose-6 phosphate (G6P) into glucose. G6P will therefore build up in the liver. In type Ib, the enzyme is present and works but your body cannot access it.
In type Ia, your body struggles to release energy from any of the major sources:
You cannot release glucose into the blood stream.
Your body’s ability to use protein will be limited if G6P builds up.
Your body’s ability to use fat as an energy source will also be limited if G6P build-up in the liver.
With your body struggling to generate energy from the usual sources, it starts to make energy in other ways.
It can use G6P to make substances called lactate, which can be used to some extent for energy, and urate. High levels of both lactate and urate need to be addressed as, over time, they can be damaging to the kidneys and can also cause other issues.
Good dietary management aims to reduce the risk of your blood glucose levels going too low. This will mean that your body will not need to generate lactate or urate.
Medication can be used alongside dietary management to help reduce urate levels.
Many individuals with type Ib also have additional symptoms. This is because they can develop an additional condition called neutropenia. Neutropenia means ‘low levels of white blood cells’ which are important for the immune system.
This can lead to gut and intestinal symptoms in type Ib such as mouth ulcers and sometimes inflammation (pain, swelling) of the bowel.
To help alleviate some of the symptoms of neutropenia, individuals with GSD type Ib should;