Gaucher Disease Types
There are three types of Gaucher disease. The most common forms of Gaucher disease (Type 1) affects 1 in 100,000 of the general population, although not all those who inherit the mutated genes for this disorder will show symptoms.
Neuronopathic forms of Gaucher Disease (nGD)
In all forms of Gaucher Disease, there is a build-up of glucocerebroside in the liver and spleen. In addition, in patients with types 2 and 3, there is accumulation within the nervous system. This is also seen in type I but does not cause any obvious problems. Certain areas seem to be more affected than others.
Particularly important is the brainstem. This is located just below the cerebral hemispheres. It has many important functions - two particularly so. The vital centres (controlling breathing and heart rate) are located here. Also most of the cranial nerves (the nerves to the face and neck) originate from here. Other areas that seem to be involved are the cerebellum and the basal ganglia, which control balance, posture and movement.
Why does Gaucher disease affect the nervous system in some people but not on others?
There is no clear explanation for this, although there are several theories. However, none of them has been proven.
One theory that seems to be fairly plausible has to do with is the origin of glucocerebroside. Most of the glucocerebroside (we will call it GC for short) in our body comes from the membranes of blood cells that have reached the end of their natural lives and have to be broken down. However, the GC in the brain is formed from other compounds called gangliosides. This much is definite. The theory is that in type I Gaucher disease there is enough enzyme to break down this GC and so it protects the brain. However, in types 2 and 3 the enzyme levels are too low to break down the GC. As a result it builds up and that is why neurological problems occur in such patients. This theory has not yet been proven but it seems to make sense.
There has also been a lot of interest in the role of calcium. It seems that for the correct functioning of nerve cells, calcium balance is critical. Accumulation of GC seems to upset this balance and cause nerve cells to die. It looks as though this happens only in NGD. However, why this should be the case, or exactly how calcium and glucocerebroside are related, are questions that remain to be answered?