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 gets into the cells, but has no transporter out. Because of the defect in transportation, the cell crystallizes causing early cell death. Cystinosis 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. And yet research on complicated diseases like cystinosis often leads to advancements in other rare diseases.
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.
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 crystallize within tissue. The cystine content of the cell is 50-100 times the normal value.
Cystinosis is a rare, incurable metabolic disease that afflicts 500 children and young adults in the United States and only 2000 worldwide. The amino acid cystine accumulates and crystallizes in cells due to abnormal transport of the cystine. This build up eventually destroys all the body’s organs including the kidneys, liver, muscles, white blood cells, eyes and central nervous system.
Read about the diagnosis of cystinosis
Symptoms and Effects
There are three clinical forms of cystinosis. Infantile (nephropathic) cystinosis; late-onset cystinosis; and benign cystinosis. Infantile cystinosis is the most severe and the most common type of cystinosis. Children with nephropathic cystinosis appear normal at birth but by 9-10 months of age, have symptoms that include excessive thirst and urination and failure to thrive. Children often appear pale and thin and have short stature. The abnormally high loss of phosphorous in the urine leads to rickets.
About the symptoms and effects of cystinosis
Fanconi Syndrome is treated symptomatically. Fanconi Syndrome causes a loss of minerals and nutrients in the urine. Treatment requires free access to water and oral replacement of salts and minerals that are lost in the urine. High doses of vitamin D and phosphate are required to replace the lost nutrients and minerals and to prevent rickets.
More about the treatment of cystinosis