This assay measures the activity of enzymes associated with 6 lysosomal storage disorders as well as C20, C22, C24, and C26 lysophosphatidylcholine (LPC) species in dried blood spots (DBS) by tandem mass spectrometry. The 6 enzymes are deficient or absent in Gaucher, Niemann-Pick type A and type B, Pompe, Krabbe, or Fabry disease, or mucopolysaccharidosis I. Long chain (C24 and C26) LPC species are elevated in patients with peroxisomal disorders such as X-linked adrenoleukodystrophy and peroxisomal biogenesis disorders.
Three 1/8" DBS are excised from a single specimen and placed into individual microtiter plates. One spot is treated with a cocktail containing acid sphingomyelinase-specific substrate and internal standard. To the second DBS a cocktail containing substrate and internal standard for beta-glucocerebrosidase, alpha-glucosidase, alpha-galactosidase, galactocerebrosidase, and alpha-L-iduronidase is added. The 2 enzyme plates are sealed and incubated for 19 hours. The third DBS is extracted with methanol containing d4-C26 LPC. The extract is then evaporated under heated nitrogen, reconstituted and stored refrigerated until day 2 of the procedure. Following the 19-hour incubation, the enzyme plates are combined and then purified by liquid-liquid extraction and solid-phase extraction. The purified extracts are evaporated, reconstituted in the prepared LPC plate, and analyzed by tandem mass spectrometry.(Unpublished Mayo method)