October 10, 2018
Cystinosis is an autosomal recessive lysosomal storage disease caused by CTNS gene mutations. The normal product of the CTNS gene is cystinosin, a transport protein that moves the amino acid cystine out of the lysosome. CTNS gene mutations (more than 80 have been described thus far) result in the accumulation of cystine within lysosomes. Cystine crystals, which accumulate in various tissues such as the kidney and eye, can be detected using polarization or electron microscopy (Fig. 1). In the kidney, multinucleated podocytes (Fig. 2-3) and increased numbers of atubular glomeruli (not shown) may be identified by routine light microscopy. In the eye, corneal opacities may be seen using slit lamp examination (Fig. 4). Most cases of cystinosis tend to be infantile; however, juvenile and adult forms of the disease are also recognized. The diagnosis is confirmed using genetic testing.
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David G. Cogan Ophthalmic Pathology Collection, NEI/NIH (Fig. 1 and 4).