Cystinosis is an "orphan" disease with about 500 people - mostly children - stricken with the disease in the United States and approximately 2,000 worldwide.

Cystinosis is a metabolic disease in which the amino acid cystine accumulates within the cells. The cystine slowly destroys the organs in the body including the kidneys, liver, eyes, muscles and the brain. With such a rare disease affecting such a small population, research money is scarce to nonexistent. Yet research on complicated diseases like cystinosis often leads to advancements in other rare diseases.

As proteins are degraded within the lysosomes of cells, the individual amino acids that make up the proteins are transported from the lysosome to the cell’s cytoplasm via specific transporters. The transporter for cystine is defective in children with cystinosis and this defect causes the cystine to accumulate within tissue. The cystine content of the cell is 50-100 times the normal value.

Cystinosis is an autosomal recessive genetic disease. This means that both parents are carriers of the abnormal gene that leads to this condition. The parents do not exhibit any of the symptoms of cystinosis. In such couples, the odds are that one-in-four of their children will have cystinosis. The gene for cystinosis, CTNS, was mapped to chromosome 17p13.