Cystinosis is a rare, incurable metabolic disease that afflicts 500 children and young adults in the United States and only 2000 worldwide.
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, which causes the cystine to crystallize within tissues. This build up eventually destroys all the body’s organs including the kidneys, liver, muscles, white blood cells, eyes and central nervous system.
Cystinosis is a common cause of the Fanconi Syndrome, a renal tubular disease. By about one year of age, patients eliminate large volumes of urine and lose large amounts of salt and other minerals in their urine.
Without specific treatment, these children progress to end-stage renal failure by an average age of nine years. In the past, this meant death. Today these patients can receive renal dialysis or transplantation, but even with successful transplantations, they develop abnormalities in other organs.
Fortunately, the drug cysteamine slows the progression of cystinosis by removing the cystine from cells, but for the drug treatment to be effective, it must be taken every six hours. Although this has led to a much better future for these children, cysteamine is not a cure.
Cystinosis is an autosomal recessive genetic disease, which means that both parents are carriers of the abnormal gene that leads to this condition. In such couples, the odds are one in four that their children will have cystinosis.