Cystinosis is a condition where cystine precipitates as a solid in various organs.  This accumulation interferes with bodily function and can be fatal. This disorder can be resolved by treatment with cysteamine. Cysteamine acts to solubilize the cystine by (1) forming the mixed disulfide cysteine-cysteamine, which is more soluble and exportable, and (2) reducing cystine to cysteine.