Table 1.

Lysosomal enzyme activities in ISSD

Cultured fibroblast enzyme activities (nmol/h/mg)
Enzyme	Reference interval	Patient 1	Patient 2
Neuraminidase	11.9–20.1	181	199
β-Galactosidase	335–435	629	789
β-Glucuronidase	105–233	95 (93)	141
β-Glucocerebrosidase	71–108	237	NA
Sphingomyelinase	56–113	158	NA
Arylsulfatase A	22–50	70	78
Acid lipase	NA	801	1,108
α-Mannosidase	64–184	50	146
Total hexosaminidase	8160–11,500	18,329	20,018
Hexosaminidase A	390–750	1,925	2,155

Serum hexosaminidases (nmol/h/mL)
Enzyme	Reference interval	Patient 1
Total serum hexosaminidase	439–1,300	572
Serum hexosaminidase A	30–45 % of total	249 (43.5 % of total)

Lysosomal enzyme activities were measured from cultured skin fibroblast extracts in the laboratory of Dr. T. Rupar according to standard methods, in triplicate with simultaneous triplicate measurement of a same-day control specimen. Skin biopsy for fibroblast culture was obtained antemortem in Patient 1, and postmortem in Patient 2. Serum hexosaminidases were tested at the Hospital for Sick Children, Toronto, Canada, according to standard methods

NA Not available