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)
