8. Leucocytes and plasma (also possible in fibroblasts): measuring lysosomal enzymes of ß-Glucocerebrosidase (Gaucher), N-Acetyl-Glukosamin-6-Sulfatsulfatase (MPS IVA), ß-Glucoronidase (MPS VII), Neuraminidase and ß-Galactosidase (Galactosialidosis, GM1 Gangliosidosis and Sialidosis) Ceramidase (Farber disease). Acid lipase (Wolman disease), Sphingomyelinase (NPA). This evidence concerns the gene GBA1 and sialidosis.