In the course of normal life there is a continuous recycling process of building new materials and breaking down old ones ready for disposal. This activity takes place in a special part of the body’s cells called the lysosome. This process requires a series of biochemical tools called enzymes. Enzymes can only reach the lysosomes after a special signal has been attached to them.
In children with ML III this signal is not attached so the enzymes are unable to get to the right place and are therefore lost outside the cell. Babies may show little sign of the disease, but symptoms start to appear as more and more cells become damaged by the accumulation of unwanted molecules.