Management dilemmas in pediatric nephrology: Cystinosis.

BACKGROUND: Cystinosis is a rare, inherited autosomal recessive disease caused by the accumulation of free cystine in lysosomes. It is treated by the administration of cysteamine, which should be monitored by trough white blood cell (WBC) cystine measurements to ensure effective treatment. CASE-DIAGNOSIS/TREATMENT: The index case had an older brother who had previously been diagnosed with cystinosis, allowing early diagnosis of the index case at the age of 5 months. Cysteamine therapy was started at the age of 3 years; however, monitoring of WBC cystine levels did not occur on a regular basis during most of his life. Growth retardation improved after correction of electrolyte disturbances, the initiation of cysteamine therapy and treatment with recombinant human growth hormone. Renal replacement therapy was started at the age of 11 years, and renal transplantation was performed at the age of 12 years. Extra-renal cystine accumulation caused multiple endocrinopathies (including adrenal insufficiency, hypothyroidism and primary hypogonadism), neurological symptoms, pancytopenia owing to splenomegaly and portal hypertension due to nodular regenerative hyperplasia, aggravated by splenic vein thrombosis and partial portal vein thrombosis. The patient died of diffuse intra-abdominal bleeding caused by severe portal hypertension.
CONCLUSION: Cysteamine treatment should be started as early as possible, and dosage should be monitored and adapted based on trough WBC cystine levels. RELEVANT INTERNATIONAL GUIDELINE: Emma F et al. (2014) Nephropathic cystinosis: an international consensus document. Nephrol Dial Transplant 29:iv87-iv94.