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.
Conclusion: 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.
Competing interests: None declared
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Communicated by: Ertan Mayatepek, MD
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Synopsis
The indications, optimal dose regimen, and efficacy of l-carnitine supplementation in cystinosis are unknown; however, current dosing schemes result in over-supplementation.
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All the authors of this chapter declare that there are no conflicts of interest.
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All procedures followed were in accordance with the ethical standards of the responsible committee on human experimentation (institutional and national) and with the Helsinki Declaration of 1975, as revised in 2005. Informed consent was obtained from all patients for being included in the study.
Details of the Contributions of Individual Authors
Martine Besouw planned the study, gathered data, and wrote the manuscript.
David Cassiman interpreted data and corrected the manuscript.
Elisabeth Cornelissen conducted the study and corrected the manuscript.
Leo Kluijtmans interpreted data and corrected the manuscript.
Lambertus van den Heuvel interpreted data and corrected the manuscript.
Elena Levtchenko supervised the study, planned the study, and corrected the manuscript.
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Besouw, M., Cornelissen, E., Cassiman, D., Kluijtmans, L., van den Heuvel, L., Levtchenko, E. (2014). Carnitine Profile and Effect of Suppletion in Children with Renal Fanconi Syndrome due to Cystinosis. In: Zschocke, J., Gibson, K., Brown, G., Morava, E., Peters, V. (eds) JIMD Reports Volume 16. JIMD Reports, vol 16. Springer, Berlin, Heidelberg. https://doi.org/10.1007/8904_2014_312
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DOI: https://doi.org/10.1007/8904_2014_312
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