title: A 6-year-old boy with hyperammonaemia: partial N-acetylglutamate synthase deficiency or portosystemic encephalopathy?
abstract: We describe a 6-year-old boy admitted with lethargy and somnolence. Laboratory tests showed hyperammonaemia (arterial level 186 micromol/l) and slightly elevated prothrombin time. The patient was treated with sodium benzoate, lactulose and a protein-restricted diet. This resulted in an insufficient decrease in blood ammonia levels. Metabolic investigations were unrevealing apart from a slightly elevated urinary glutamine concentration. Liver tissue showed steatosis and mildly decreased activity of N-acetylglutamate synthase suggesting partial deficiency. Treatment with N-carbamyl glutamate did not affect serum ammonia levels. Colour Doppler sonography and MR angiography demonstrated a patent ductus venosus. After surgical ligation of the ductus venosus, serum ammonia levels returned to normal and mental and motor performance improved markedly.
  
  
  CONCLUSIONS
  In late onset hyperammonaemia, partial N-acetylglutamate synthase deficiency and portocaval shunt should be ruled out.
authors.affiliation: Department of Paediatric Neurology, Academic Hospital, Free University of Amsterdam, The Netherlands. mvwegen@xs4all.nl
authors.forename: D
authors.initials: D
authors.lastname: Broere
authors.forename: W G
authors.initials: WG
authors.lastname: van Gemert
authors.forename: C M
authors.initials: CM
authors.lastname: Kneepkens
authors.forename: D M
authors.initials: DM
authors.lastname: Neele
authors.forename: R A
authors.initials: RA
authors.lastname: Manoliu
authors.forename: J A
authors.initials: JA
authors.lastname: Rauwerda
authors.forename: M S
authors.initials: MS
authors.lastname: van der Knaap
mesh_terms: D000123:Acetyltransferases / Q000172:deficiency* / Q000378:metabolism; D051046:Amino-Acid N-Acetyltransferase; D001921:Brain / Q000473:pathology; D002648:Child; D006501:Hepatic Encephalopathy / Q000150:complications / Q000175:diagnosis* / Q000601:surgery; D006801:Humans; D022124:Hyperammonemia / Q000209:etiology*; D008279:Magnetic Resonance Imaging; D008297:Male; D008661:Metabolism, Inborn Errors / Q000150:complications / Q000175:diagnosis*
chemical_list: D000123:Acetyltransferases; D051046:Amino-Acid N-Acetyltransferase; C494874:NAGS protein, human