Secondary carnitine deficiency in hyperammonemic attacks of ornithine transcarbamylase deficiency

Carnitine status was evaluated in 12 patients with hyperammonemic attacks caused by a deficiency in ornithine transcarbamylase. We found decreased free carnitine and increased acylcarnitine levels in the serum, a decreased free carnitine content and an elevated acyl/free carnitine ratio in the liver, and increased excretion of free and acylcarnitine in the urine. Analyses of urinary acylcarnitine using the secondary ion mass spectrometry technique revealed increased amounts of acetylcarnitine and dicarboxylic acid derivatives. These data suggest that the patients had a secondary carnitine deficiency, possibly an aggravating factor in urea cycle dysfunction. After oral administration of L-carnitine (50 to 100 mg/kg/d) in two patients, hyperammonemic episodes were less frequent. Blood ammonia levels decreased significantly, accompanied by an increase in serum free carnitine levels.