Nephropatic cystinosis (NC) is a rare disease associated with pathogenic 
variants in the CTNS gene, with a common variant that consists of a 
57kb-deletion involving CTNS. Patients with NC that are treated with cysteamine 
improve their life quality and expectancy. We report a 12-month-old girl with a 
poor growth rate since the 4th month of life. She was admitted to the Hospital 
with acute kidney injury, severe dehydration and metabolic acidosis. She was 
treated with volume restorative and bicarbonate. Proximal tubulopathy and 
Fanconi's syndrome was diagnosed. Medical treatment improved renal function that 
was stabilized in stage 4 chronic kidney disease (CKD). Since infantile NC was 
suspected, CTNS genetic analysis was considered. Genomic DNA was isolated from 
peripheral blood to perform PCR for exons 3-12 in CTNS gene and for the specific 
57kb-deletion PCR. Afterwards, variant segregation analysis was performed in the 
familiar trio. The genetic analysis showed that the patient was homozygous for 
the common 57kb-deletion encompassing CTNS that had been inherited from her 
asymptomatic heterozygous parents. The molecular confirmation allowed genetic 
counselling for parents and facilitated the access to cysteamine. Oral treatment 
with cysteamine resulted in improvement of renal function to CKD stage 3. After 
16 months of treatment the patient shows metabolic stability and mild recovery 
of height. Ophthalmologic follow-up detected ocular cystine crystals 12 months 
after diagnosis, starting cysteamine drops.