Nephropathic cystinosis: pathophysiology and effects of treatment

Nephropathic cystinosis is a rare inherited disease characterized by cristallization of cystine in lyzosomes. Cystine accumulation is caused by the mutations in the CTNS gene encoding for cystinosine, a cystine transporter. Cystinosis commonly affects the kidneys leading to renal Fanconi sysnrome during the first year of life, followed by progressive kidney failure that necessitates initiation of renal replacement therapy in childhood or adolescence. In adulthood, patients also present with various systemic manifestations including photophobia, hypothyroidism, diabetes mellitus, hypogonadism (in males), myopathy, neurological disorders. Corneal crystal accumulation can be detected in all patients with cystinosis by slit-lamp examination. A diagnosis of cystinosis can be confirmed by measuring cystine levels in white blood cells and genetic testing. Early diagnosis is of vital importance given the availability of cysteamine, the specific cystinedepleting therapy, that delays the onset of end-stage renal disease and extrarenal manifestations.