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The Fish

Cystinosis

Cystinosis is caused by mutations in the CTNS gene encoding for the carrier protein cystinosin that has the task to transport cystin out of the lysosomal compartment. A defect of the cystinosin function results in intra-lysosomal cystin accumulation in all cells. First of all the kidneys are affected, starting with proximal tubular damage during the first year of life, followed by end-stage renal failure during mid-childhood. Also the eyes, thyroid, pancreas and muscles are affected. In some older patients also the CNS can be involved.

Etiology: - Defective cystinosin leads to transportation disorder of cystine from lysosome
Gene: CTNS Gene
Mode of inheritance: Autosomal recessive
Phenotypes:

Infantile nephropathic form
Juvenile nephropathic form
Ocular form

Leading symptoms:
Infantile nephropathic form
(Age of onset: 6-12 months)

Symptoms of Fanconi-Syndrome: Polyuria, polydipsia, Vitamin D refractory rachitis
Progressive renal insufficiency
Failure to thrive

Juvenile nephropathic form
(Age of onset: childhood, adolescence)

Symptoms of Fanconi-Syndrome: Polyuria, polydipsia, Vitamin D refractory rachitis
Progressive renal insufficiency
Delay in height and weight increase
Cystine cristals in cornea and conjunctiva

Ocular form

Cystine cristals in cornea and conjunctiva
Photophobia
Retinopathy

Diagnostics:

Determination of elevated intracellular cystine levels in blood
Molecular genetic analysis of CTNS Gene

Therapy: Cysteamin (Cystagon®)