There is a 25% risk of having a child with the disorder, when both parents are carriers of an autosomal recessive trait. Cystinosis affects approximately 1 in 100,000 to 200,000 newborns. and there are only around 2,000 known individuals with cystinosis in the world. The incidence is higher in the province of Brittany, France, where the disorder affects 1 in 26,000 individuals. Diagnosis
Cystinosis is a rare genetic disorder that causes an accumulation of the amino acid cystine within cells, forming crystals that can build up and damage the cells. These crystals negatively affect many systems in the body, especially the kidneys and eyes.The accumulation is caused by abnormal transport of cystine from lysosomes, resulting in a massive intra-lysosomal cystine accumulation in tissues. Via an as yet unknown mechanism, lysosomal cystine appears to amplify and alter apoptosis in such a way that cells die inappropriately, leading to loss of renal epithelial cells. This results in renal Fanconi syndrome, and similar loss in other tissues can account for the short stature, retinopathy, and other features of the disease. Definitive diagnosis and treatment monitoring are most often performed through measurement of white blood cell cystine level using tandem mass spectrometry. Types
Online Mendelian Inheritance in Man (OMIM): 219800 – Infantile nephropathic
Online Mendelian Inheritance in Man (OMIM): 219900 – Adolescent nephropathic
Online Mendelian Inheritance in Man (OMIM): 219750 – Adult nonnephropathic

Treatment
Cystinosis is normally treated with cysteamine, which is available in capsules and in eye drops.
The signs and symptoms of intermediate cystinosis are the same as nephropathic cystinosis, but they occur at a later age. Intermediate cystinosis typically begins to affect individuals around age twelve to fifteen. Malfunctioning kidneys and corneal crystals are the main initial features of this disorder. If intermediate cystinosis is left untreated, complete kidney failure will occur, but usually not until the late teens to mid twenties. People with non-nephropathic or ocular cystinosis do not usually experience growth impairment or kidney malfunction. The only symptom is photophobia due to cystine crystals in the cornea. Crystal morphology and identification
Cystine crystals are hexagonal in shape and are colorless. They are not found often in alkaline urine due to their high solubility. The colorless crystals can be difficult to distinguish from uric acid crystals which are also hexagonal. Under polarized examination, the crystals are birefringent with a polarization color interference. Genetics
Cystinosis occurs due to a mutation in the gene CTNS, located on chromosome 17, which codes for cystinosin, the lysosomal cystine transporter. Symptoms are first seen at about 3 to 18 months of age with profound polyuria (excessive urination), followed by poor growth, photophobia, and ultimately kidney failure by age 6 years in the nephropathic form. All forms of cystinosis (nephropathic, juvenile and ocular) are autosomal recessive, which means that the trait is located on an autosomal chromosome, and only an individual who inherits two copies of the gene – one from both parents – will have the disorder.