Primary systemic carnitine deficiency under successful therapy: clinical, biochemical, ultrahistochemical and renal clearance studies.

Systemic carnitine deficiency is an often fatal, but treatable metabolic disorder which should be considered in any child with repeated episodes of a Reye-like syndrome or a cardiomyopathy. A 4-year-old girl with a typical history and clinical findings was successfully treated with oral carnitine. Despite low liver carnitine, ketogenesis upon fasting was normal. Normal muscle function under therapy was associated with unchanged low muscle carnitine levels. Improvement of mitochondrial structure and function was demonstrated by controlled ultrahistochemical studies. A renal carnitine leak, evident from renal clearance studies, may contribute to the pathogenesis of systemic carnitine deficiency.