Cystinosis

Cystinosis is a rare autosomal recessive lysosomal storage disorder caused by mutations in the CTNS gene, which encodes the cystinosin protein. This disorder affects an estimated 1 in 100,000 to 200,000 live births worldwide. Cystinosis is characterized by the accumulation of cystine within cellular lysosomes, ultimately affecting almost all organs.

Renal involvement, characterized by proximal tubulopathy, is the most common cause of morbidity and mortality in nephropathic or infantile cystinosis and eventually leads to renal failure. Cystinosis is also the most common inherited cause of Fanconi syndrome in children. The 3 known forms of cystinosis are infantile (nephropathic), juvenile (intermediate and late-onset), and adult (benign, ocular, and non-nephropathic).

The infantile form is the most common and severe, accounting for about 95% of cases, and typically leads to end-stage renal disease (ESRD) by ages 10 to 12. Cysteamine, a cystine-depleting therapy, is the cornerstone of treatment for this disorder. Early recognition and treatment with cysteamine can delay the progression to ESRD and associated morbidities, resulting in improved overall outcomes.