Lysosomal storage diseases

Lysosomal storage diseases are a group of around 40 different inherited diseases that affect children and adults. They share common patterns of biochemical and clinical defects. These disorders result mainly from enzyme abnormalities in the metabolism and catabolism of complex neurolipids and mucopolysacchari des. They are in a class of diseases called inborn-errors of metabolism -- in this case the error results primarily from the absence of an enzyme whose target is a substance to be discarded from cellular tissues. The buildup, or "storage," of such substances causes a loss of function in one or several crucial areas of the body. This may result in mental and physical disability or, in most cases, shortened lifespan.

Lysosomes are a cell's 'recycling centres'. Their role is to break down complex material to simple products for recycling within the cell to build new complex material. The degradation pathway is a very regimented, stepwise reaction. The molecules collected by the lysosomes are extremely large and made of several different components. Each component requires a specific enzyme or chemical in order for it to be removed. Each component must be removed from the long chain before the next one can be. Irregularities in the stepwise process, usually due to the absence or deficiency of a specific enzyme, breaks this process chain and can result in storage of intermediate materials within the lysosome. Over time, the level of storage in the lysosome increases and leads to severe physical symptoms as the material builds up in the body.

The estimated incidence of lysosomal storage disorders in the Australian population is 1 in 5,000 births, leading to 50 new cases in Australia each year.