It is one of a number of lysosomal storage diseases. Lysosomes are structures within cells that are responsible for breaking down and recycling unwanted cellular components and produce a number of key enzymes that are involved in this recycling process. Mutations in specific genes affect the efficiency of this process and cause the accumulation of intermediate chemicals to levels that can be toxic to cells, particularly to neuronal (nerve) cells. This leads to progressive neurodegeneration (degeneration of brain and eye cells) and results in severe neurological impairment and early death.