Urinary lipid profiling for the identification of fabry hemizygotes and heterozygotes

Background: Fabry disease is an X-linked lysosomal storage disorder resulting from a deficiency of the lysosomal hydrolase, α-galactosidase, for which enzyme replacement therapy is now available. In this study, we aimed to identify Fabry heterozygotes not only for genetic counseling of families but because it is becoming increasingly obvious that many heterozygous (carrier) females are symptomatic and should be considered for treatment. Methods: We measured 29 individual lipid species, including ceramide, glucosylceramide, lactosylceramide, and ceramide trihexoside, in urine samples from Fabry hemizygotes and heterozygotes and from control individuals by electrospray ionization tandem mass spectrometry. Individual analyte species and analyte ratios were analyzed for their ability to differentiate the control and patient groups. Results: The Fabry hemizygotes had increased concentrations of the substrate for the deficient enzyme, ceramide trihexoside, as well as lactosylcerainide and ceramide, along with decreased concentrations of both glucosylceramide and sphingomyelin. Ratios of these analytes improved differentiation between the control and Fabry groups, with the Fabry heterozygotes generally falling between the Fabry hemizygotes and the control group. Conclusions: These lipid profiles hold particular promise for the identification of Fabry individuals, may aid in the prediction of phenotype, and are potentially useful for the monitoring of therapy in patients receiving enzyme replacement.