Clinical practice recommendations for the diagnosis and management of nephropathic cystinosis

Cystinosis is a rare autosomal recessive lysosomal storage disorder caused by pathogenic variants in CTNS, which encodes cystinosin, a H⁺/cystine symporter that mediates cystine efflux from lysosomes. Defective cystinosin leads to accumulation of cystine in lysosomes and the formation of cystine crystals in most tissues. In its more severe and frequent form, infantile nephropathic cystinosis, patients present with renal Fanconi syndrome in the first 2 years of life, which progresses to chronic kidney disease. Since the 1970s, cysteamine therapy and improvements in dialysis and transplantation have substantially improved patient outcomes, and currently most patients survive into adulthood. Consequently, the diagnosis and management of extra-renal complications that develop later in life have become increasingly important. In addition to the kidneys, commonly affected organs include the eyes, the musculoskeletal system, the central nervous system, exocrine glands and endocrine organs. Cystinosis therefore requires integrated care that involves multiple medical specialties and a structured transition plan from paediatric to adult care. Herein, we present evidence-based and expert opinion-based clinical practice recommendations, developed by a team of international specialists and patient representatives following the GRADE methodology, to improve the diagnosis and management of cystinosis in children and adults.