Cystinosis, an autosomal recessive disorder of lysosomal
cystine accumulation, results from mutations in the CTNS gene that encodes the lysosomal
cystine transporter, cystinosin. Renal tubular
Fanconi syndrome occurs in infancy, followed by
rickets, growth retardation,
photophobia, and
renal failure, which requires
renal transplantation at approximately 10 yr of age. Treatment with
cysteamine decreases cellular
cystine levels, retards renal deterioration, and allows for normal growth. Patients with a history of inadequate
cystine depletion
therapy may survive, after
renal transplantation, into the third to fifth decades but will experience other, extrarenal complications of the disease. Routine chest and head computed tomography scans of 41 posttransplantation patients with
cystinosis were reviewed for
vascular calcification. The radiologic procedures had been performed to examine lung and brain parenchyma, so there was little ascertainment bias. Thirteen of the 41 patients had
vascular calcification, including 11 with coronary artery calcification. One 25-yr-old man required three-vessel coronary artery bypass graft surgery. There were no significant differences between the 13 patients with calcification and the 28 without calcification in the following parameters: Time on dialysis, frequency of
transplantation,
hypertension,
hypercholesterolemia, homozygosity for the 57-kb deletion in CTNS, serum
creatinine, and
calcium-phosphate product. However, the finding of
vascular calcification correlated directly with duration of life without
cysteamine therapy and inversely with duration of life under good
cystine-depleting
therapy. The accumulation of intracellular
cystine itself maybe a risk factor for
vascular calcifications, and older patients with
cystinosis should be screened for this complication.