Nephropathic cystinosis (also known as infantile cystinosis) is an autosomal recessive inherited lysosomal storage disease that leads to the deposition of cystine crystals in various organs. The kidneys, spleen, liver, eyes and bone marrow are the most affected.
In addition to the juvenile and ocular form, infantile cystinosis is the most common variant of cystinosis and manifests itself between the third and sixth month of life. The children suffer from loss of appetite, vomiting, polyuria-polydipsia syndrome and failure to thrive with greatly reduced size and weight gain.
The primary problem is a resorption disorder in the proximal tubule (DeToni-Debré-Fanconi syndrome), which results in severe disturbances in fluid and electrolyte balance, renal acidosis and rickets.
Furthermore, the cystine deposits lead to hypothyroidism, insulin-dependent diabetes mellitus, hepatic hypertension with portal vein hypertension and to muscular and cerebral symptoms. The cornea and conjunctiva are affected ocularly, causing photophobia and increased flow of tears.
Intellectual development is usually not affected in the mostly fair-haired patients. Most children develop dialysis-dependent renal failure by the age of ten, which is caused by the progressive interstitial fibrosis and sclerosis of the kidneys.
The milder juvenile form manifests in adolescence. The ocular form shows a benign course without renal involvement and is often a random diagnosis. Cause of all clinical forms are mutations in the CTNS gene in the chromosome 17p13. This code for the lysosomal membrane protein cystinosin, which is responsible for the transport of cystine from the lysosomes.