Evaluation of urinary acylglycines by electrospray tandem mass spectrometry in mitochondrial energy metabolism defects and organic acidurias

We analyzed the urinary acylglycine excretion in 26 patients with mitochond rial energy metabolism disorders and in 55 patients with organic acidurias by electrospray tandem mass spectrometry (ESI-MS/MS), monitoring precursor ions of m/z 90. Urinary concentrations of the different acylglycines were q uantified using deuterated internal standards. Normal values for the most i mportant acylglycines were established. In MCAD and MAD (neonatal form) def iciencies, typical excretion patterns of urinary acylglycines were found in all the samples. In isovaleric aciduria, propionic aciduria, and 3-methylc rotonylglycinuria typical glycine conjugates were always found, Methylmalon ic aciduria (mutase deficiency), multiple carboxylase deficiency; and 3-hyd roxy-3-methylglutaric aciduria revealed pathological acylglycine profiles, even if not specific for the disease. In all these diseases acylglycine exc retion seems to be less influenced by the clinical status than organic acid excretion. This method is a useful diagnostic tool for these metabolic dis orders, complementary to organic acids and acylcarnitine profiles. (C) 2000 Academic Press.