Increased cystine in leukocytes from individuals homozygous and heterozygous for cystinosis.

In patients with cystinosis, the concentration of free cystine in leukocytes was 80 times greater than normal, and six times the normal content for their parents. This is the first demonstration of an abnormality in heterozygotes for this rare inherited disease of childhood. Three-quarters of the cystine was recovered in the granular fraction of cystinotic leukocytes.