Variables in the laboratory diagnosis of Fabry's disease by measurement of methylumbelliferyl α galactosidase activity

Abstract

Assay of methylumbelliferyl α galactosidase activity (MUM α Galase) in plasma reflects the activity of ceramide trihexosidase and (or) ceramide digalactosidase, which are deficient in Fabry's disease. Intending to institute this assay routinely, substrate stability and concentration, sample stability, heat inactivation conditions, and normal values were evaluated. The heat labile isoenzyme(s) deficient in plasma from patients with Fabry's disease must either be assayed immediately after sampling or the plasma must be stored at or below -50 °C. This heat labile fraction can be inactivated by incubating a plasma aliquot at 45°C for 45 min. Normal adult ranges for total and heat labile MUM α Galase are 8.9-31.7 and 7.4-27.4 nmoles of MUM per hr per ml of EDTA treated plasma.