Lysosomes are intracellular sacs of enzymes that are responsible for the digestion of macromolecules. The products of the hydrolytic digestion process then leave the lysosome via specific transporters in its membrane, to be either reused by the cell or excreted outwards. The general consensus about cystinosis has been that it is an inherited multi-systemic disease resulting from failure of lysosomal cystine transport. However, it has only been since the cloning of the causative gene, CTNS (short for cystinosis), and the study of the encoded protein, cystinosin, that the molecular basis of this disorder has been understood.