Renal handling of free and acylcarnitine in secondary carnitine deficiency

Free and acylcarnitine in serum and urine samples were measured in miscellaneous diseases, including mitochondrial cytopathy with Fanconi's syndrome (MCFS). The urinary concentration of acylcarnitine always exceeded that of free carnitine, and a significant negative correlation was found between the ratio of serum free to acylcarnitine and the ratio of free to acylcarnitine clearance among control and test patients (p less than 0.005). A patient with MCFS excreted large amounts of free carnitine compared with acylcarnitine in urine, which may be attributable to decreased reabsorption of free carnitine in renal tubules.