Cystinosis is a lysosomal storage disease with accumulation of cystine within lysosomes. The diagnosis can be established using diagnostic testing.

Identification of elevated cystine within cells:

(1) neutrophils (by mass spectrometry)

(2) cultured fibroblasts

(3) placenta


Demonstration of cystine crystals:

(1) cornea (using slit lamp in infant or young child; should be present after 16 months of age)


Demonstration of a mutation:

(1) CTNS (17p13.2, gene product cystinosin)

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