Cystinosis.

Cystinosis is a very rare autosomal recessive lysosomal storage disorder with an incidence of 1 : 150,000 - 1 : 200,000, and is caused by mutations in the CTNS gene encoding the lysosomal membrane protein cystinosin, which transports cystine out of the lysosome into the cytoplasm. As a result, accumulation of cystine occurs in almost all cells and tissues, especially in the kidneys, leading to multiple organ involvement. Introduction of drug therapy with cysteamine in the mid 1980s, along with the availability of renal replacement therapy in childhood, have dramatically improved patient outcome. Whereas patients used to die without therapy with end-stage renal failure during the first decade of life, nowadays most patients live well into adulthood without renal replacement therapy, and several reach 40 years. There is robust evidence that early initiation and sustained lifelong therapy with cysteamine are both essential for morbidity and mortality. The rarity of the disease and the multi-organ involvement present an enormous challenge for those affected and the providers of care for this patient group.