title: Is globotriaosylceramide a useful biomarker in Fabry disease?
abstract: OBJECTIVE
  The aim of this study was to determine whether globotriaosylceramide (Gb3) is a useful biomarker in Fabry disease.
  
  
  METHODS
  The levels of Gb3 were measured in plasma and urine by tandem mass spectrometry in untreated hemizygotes and heterozygotes with Fabry disease and in healthy controls, and the levels were monitored in patients on treatment with enzyme replacement therapy (ERT).
  
  
  RESULTS
  Hemizygotes with classic Fabry disease showed elevated levels of Gb3 in both plasma and urine and could readily be distinguished from normal controls. Male patients with the N215S mutation had normal levels in their plasma but 50% had marginally elevated levels in their urine. Thirty-three percent of proven heterozygotes had elevated Gb3 concentrations in plasma but 97% of those without the N215S mutation (36/37) had an elevated level in urine. The four heterozygotes with the N215S mutation had normal Gb3 levels in urine. The level of Gb3 in plasma initially fell following the start of ERT in all patients who had an elevated level before treatment. However, in a few patients the level subsequently rose. Similar results were found for the levels of Gb3 in urine.
  
  
  CONCLUSIONS
  Gb3 is not an ideal marker of Fabry disease or the response to treatment in all patients. Plasma and urine levels of Gb3 cannot be used as a marker of Fabry disease in patients with the N215S mutation and many heterozygotes do not have elevated Gb3 levels in plasma. The urine concentration is more informative in heterozygotes and can be used as a measure of the response to therapy. The fall in Gb3 levels in patients receiving ERT was not sustained in some patients, despite a clinical improvement. Additionally, Gb3 cannot be used to monitor the response to treatment in patients who initially have normal plasma and urine concentrations of this glycolipid.
authors.affiliation: Biochemistry, Endocrinology and Metabolism Unit, Institute of Child Health, University College London, London, UK. E.Young@ich.ucl.ac.uk
authors.forename: E
authors.initials: E
authors.lastname: Young
authors.forename: K
authors.initials: K
authors.lastname: Mills
authors.forename: P
authors.initials: P
authors.lastname: Morris
authors.forename: A
authors.initials: A
authors.lastname: Vellodi
authors.forename: P
authors.initials: P
authors.lastname: Lee
authors.forename: S
authors.initials: S
authors.lastname: Waldek
authors.forename: B
authors.initials: B
authors.lastname: Winchester
mesh_terms: D015415:Biomarkers; D041321:Chromosomes, Human, X / Q000235:genetics; D000795:Fabry Disease / Q000097:blood* / Q000188:drug therapy / Q000652:urine*; D005260:Female; D006017:Glycolipids / Q000378:metabolism; D006579:Heterozygote; D006720:Homozygote; D006801:Humans; D008297:Male; D013058:Mass Spectrometry; D017354:Point Mutation / Q000235:genetics; D014281:Trihexosylceramides / Q000097:blood* / Q000652:urine*; D000519:alpha-Galactosidase / Q000627:therapeutic use
chemical_list: D015415:Biomarkers; D006017:Glycolipids; D014281:Trihexosylceramides; C018549:globotriaosylceramide; D000519:alpha-Galactosidase