Gaucher and Niemann–Pick diseases—enzymatic diagnosis in dried blood spots on filter paper: retrospective diagnoses in newborn-screening cards

Background: Gaucher disease (GD) and Niemann–Pick (NP) disease are caused by deficient activity of the lysosomal enzymes acid β- d-glucosidase (ABG) and acid sphingomyelinase (ASM), respectively. For diagnosis, these enzymes are usually measured in the extracts of leukocytes or cultured fibroblasts. Chitotriosidase (CTE), a chitinolytic enzyme, is markedly increased in the plasma of Gaucher patients. We describe methods for the assay of acid β- d-glucosidase, acid sphingomyelinase, chitotriosidase, and α- N-acetyl-galactosaminidase (NAGA) as a control enzyme in blood spots that were dried onto filter paper. Methods: To tubes containing a 3 mm-diameter blood spot, we added elution liquid and substrate solution. After incubation at 37 °C, the amount of hydrolyzed product was compared with a calibrator to allow the quantification of enzyme activity. We examined 80 healthy controls, 54 Gaucher patients, 8 Niemann–Pick patients, 27 obligate carriers, and the newborn-screening cards (NSC) from a case of Gaucher and a case of Niemann–Pick disease. Results and conclusion: The described methodology is useful to identify Gaucher and Niemann–Pick patients and controls, using samples that are sufficiently stable to be transported to the testing laboratory by mail. The diagnosis of both diseases on a newborn-screening card was clearly established. The newborn-screening card has been added to the biological materials that allow the identification of patients with Gaucher and Niemann–Pick diseases.