Lysosomal transport disorders.

In the group of lysosomal storage diseases, transport disorders occupy a special place because they represent rare examples of inborn errors of metabolism caused by a defect of an intracellular membrane transporter. In particular, two disorders are caused by a proven defect in carrier-mediated transport of metabolites: cystinosis and the group of sialic acid storage disorders (SASD). The recent identification of the gene mutations for both disorders will improve patient diagnosis and shed light on new physiological mechanisms of intracellular trafficking.