[Cystinosis from childhood to adulthood]

Abstract

Nephropathic cystinosis is a metabolic disease related to lysosomal cystine accumulation in almost all tissues of the body. The first symptoms set up from 5 or 6 months of age including anorexia vomiting polyurodipsia and failure to thrive associated with a proximal tubulopathy (glycosuria, tubular proteinuria, loss of bicarbonate, potassium, phosphorus, etc.) Treatment by cysteamine dramatically changed the prognostic. If started early this treatment allows to delay and possibly to prevent the spontaneous evolution towards end stage renal disease between 6 and 12 years of age and to avoid the growth failure. On the long term the disease involves other organs: eyes, thyroid endocrine pancreas, muscle and central nervous system. The diagnosis of cystinosis is based on the cystine leukocyte assay allowing also the follow up and the adjustment of the treatment. Prenatal diagnosis is possible on chorionic sample. The gene of this recessive disease, mapping on chromosome 17 was recently identified. This gene encodes a protein of the lysosomal membrane involved in the transport of cystine out of the lysosome. There is a juvenile, late onset, form of cystinosis its main symptom is proteinuria with variable tubular alterations. The so called adult form is asymptomatic its only symptom is corneal deposits most often found by chance examination.