Lysosomal storage disorders are inherited conditions which arise from mutations in genes encoding proteins that are important for the normal function of lysosomes. The lysosome is a subcellular particle which has a very important function in the breakdown and the recycling of the macromolecular components of cells. Lysosomes are part of an endo-lysosomal network with important roles with ingestion of extra cellular material (phagocytosis), breakdown of such ingested material, inter-cellular signalling and cell death via the processes of autophagy and apoptosis. There are more than 50 lysosomal storage disorders, most of which are due to lack of an enzyme involved in the breakdown of these macro-molecules; however, some of the disorders arise through lack of other molecular components.
The LSDs are multi-system disorders which present with a complex array of clinical phenotypes. Their assessment and management requires team work across a range of different disciplines. Most of these disorders have a severe form which typically presents in childhood and milder forms which are much more prominent amongst adults. Attenuated forms which present only in adults are increasingly being recognised.
The conditions are grouped according to the biochemical characteristics of the major substance that has accumulated e.g. mucopolysacharidosis, sphingolipidosis and the glycoproteinoses. Storage of undegraded molecular material leads to cellular damage and predisposes to organ damage. Few data are available on the prevelance of LSDs, however, it is thought that one in 5-8,000 newborn may suffer from an LSD. The commonest LSD is probably Gaucher disease with a prevalence of 1 in 40,000 individuals, however, the condition is much commoner amongst the Jewish population.