title: Carnitine Profile and Effect of Suppletion in Children with Renal Fanconi Syndrome due to Cystinosis.
abstract: BACKGROUND
  Cystinosis is an autosomal recessive disorder marked by intralysosomal cystine accumulation. Patients present with generalized proximal tubular dysfunction called renal Fanconi syndrome. Urinary carnitine loss results in plasma and muscle carnitine deficiency, but no clinical signs of carnitine deficiency have been described. Also, the optimal dose of carnitine supplementation is undefined. This study aimed to determine whether currently recommended carnitine doses result in adequate correction of plasma carnitine.
  
  
  METHODS
  Five cystinosis patients with renal Fanconi syndrome, aged 2-18 years, were included. L-carnitine was prescribed 50 mg/kg/day since diagnosis: median 36 (range 18-207) months. Total and free plasma and urine carnitine and carnitine profiles were measured at study onset, after stopping L-carnitine for 3 months and 3 months after reintroducing L-carnitine 50 mg/kg/day.
  
  
  RESULTS
  At study onset, plasma free carnitine was normal in all patients, total carnitine (1/5), acetylcarnitine (3/5), and several short- and medium-chain acylcarnitines ≤10 carbons (5/5) were increased indicating carnitine over-supplementation. Three months after cessation, carnitine profiles normalized and 3/5 patients showed plasma carnitine deficiency. Three months after reintroduction, plasma free carnitine normalized in all patients, however, carnitine profiles were disturbed in 4/5 patients. Urine free carnitine, acetylcarnitine, and acylcarnitines ≤10 carbons were increased in all patients independent of carnitine supplementation.
  
  
  CONCLUSIONS
  Administration of recommended doses L-carnitine (50 mg/kg/day) resulted in over-supplementation. Although the drug is considered to be rather safe, long-term effects of over-supplementation remain unknown warranting cautious use of high doses. Plasma carnitine profile might be used as a monitor, to prevent overdosing.
authors.affiliation: Department of Pediatric Nephrology, University Hospitals Leuven, Herestraat 49, 3000, Leuven, Belgium, martine.besouw@uzleuven.be.
authors.forename: M
authors.initials: M
authors.lastname: Besouw
authors.forename: E
authors.initials: E
authors.lastname: Cornelissen
authors.forename: D
authors.initials: D
authors.lastname: Cassiman
authors.forename: L
authors.initials: L
authors.lastname: Kluijtmans
authors.forename: L
authors.initials: L
authors.lastname: van den Heuvel
authors.forename: E
authors.initials: E
authors.lastname: Levtchenko