CTNS and cystinosis: This result allows us to identify the causal mutation of cystinosis in this family: homozygous deletions carrying both exons 4 and 5 [c.(61 + 1_62–1)_(225 + 1_226–1); NM_004937.3] of the CTNS gene, according to the HGVS format (Fig. 2a).