Patients who carry a homozygous cystinosin(7Δ) mutation develop juvenile/intermediate cystinosis, while those who have one allele of cystinosin(7Δ) together with one allele of a 57 kb genomic DNA deletion at CTNS locus — the most common cystinosis mutation that leads to a complete loss of the protein — develop infantile/severe cystinosis. This evidence concerns the gene CTNS and cystinosis.