This improved diagnostic accuracy could be further increased by incorporating other markers that have similar behavior in differentiating PD from controls such as other lysosomal enzymes (acid sphingomyelinase, aSMase; acid-alpha galactosidase, GLA; acid alpha-glucosidase, GAA; galactocerebrosidase, GALC) and their relative activities, with and without association with each other [39]. The gene discussed is SMPD1; the disease is Parkinson disease.