Cystinosis

Cystinosis is a lysosomal storage disease in which the amino acid cystine builds up inside lysosomes and eventually forms crystals throughout the body, notably in the kidneys. It is inherited in an autosomal recessive pattern through mutations in the CTNS gene, which encodes cystinosin, the transporter that carries cystine out of the lysosome. The disease usually presents in infancy with renal Fanconi syndrome and, untreated, leads to end-stage kidney disease in childhood, with later effects on the eyes, thyroid, muscle, pancreas and central nervous system. It is the most common cause of Fanconi syndrome in children and was the first genetic disease documented among the lysosomal storage disorders. Treatment centers on cysteamine, which lowers cystine accumulation; early diagnosis and lifelong therapy improve growth and delay kidney failure, although survival remains shortened.