Cystinosis is a rare genetic disorder caused by a mutation in the CTNS gene, which leads to the accumulation of the amino acid cystine within cells. This buildup primarily affects the kidneys, eyes, and other organs, resulting in various health issues, including kidney dysfunction and vision problems. Symptoms of cystinosis typically appear in early childhood and may include growth delays, kidney damage, and light sensitivity due to corneal deposits. Treatment often involves medications that help reduce cystine levels, along with supportive care to manage complications associated with the disease.