Nephropathic cystinosis is an autosomal recessive lysosomal storage disorder in 
which intracellular cystine accumulates due to impaired transport out of 
lysosomes. The clinical manifestations include renal tubular Fanconi syndrome in 
the 1st year of life, with hypophosphatemic rickets, hypokalemia, polyuria, 
dehydration and acidosis, growth retardation, hypothyroidism, photophobia, renal 
glomerular deterioration by 10 years of age, and late complications such as 
myopathy, pancreatic insufficiency, and retinal blindnesss. The cystinosis gene, 
CTNS, codes for cystinosin, a 367 amino acid protein with seven transmembrane 
domains. More than 50 CTNSmutations have been identified, but approximately 50% 
of Northern European patients have a 57257-bp deletion which removes the first 
nine exons of CTNS. The mainstay of cystinosis therapy is oral cysteamine 
(Cystagon). This aminothiol can lower intracellular cystine content by 95%, and 
has proven efficacy in delaying renal glomerular deterioration, enhancing 
growth, preventing hypothyroidism, and lowering muscle cystine content. Its 
early and diligent use is critical; in one study, for every month of treatment 
prior to 3 years of age, 14 months' worth of later renal function were 
preserved. Several examples of individual patients treated early and having 
preserved renal function and normal growth are available. Newborn screening 
using a chip containing cDNA to detect common CTNSmutations may allow diagnosis 
and treatment in the first weeks of life.
CONCLUSIONS: Early diagnosis and treatment of nephropathic cystinosis can change 
the course of this disease.