Mucolipidosis III (pseudo-hurler poly dystrophy): Multiple lysosomal enzyme abnormalities in serum and cultured fibroblast cells

Four patients with the clinical findings of mucolipidosis III were studied. Cultured skin fibroblast cells from three of these four patients were low in each of the five lysosomal enzyme activities measured. The ranges of the enzyme activities in these three patients were as follows: N-acetyl-/β-glucosaminidase (11-19% of normal), β-galactosidase (26-33% of normal), α-fucosidase (31-55% of normal), a-manno- sidase (53-62% of normal), and arylsulfatase A (16-21% of normal). In contrast, marked increases in the same enzyme activities were found in serum samples from the same patients. These include N-acetyl-) β -glucosaminidase (7-16 times normal), β -galactosidase (8-11 times normal), α-fucosidase (5-10 times normal) and arylsulfatase A (14-24 times normal). Similar increases in the enzyme activities were also found in serum of patient 1; however, the changes were less dramatic. An electrophoretic analysis of one of these enzymes (N-acetyl-β-giucosaminidase) revealed an abnormal pattern in the cultured fibroblast extracts; however, the presence of a normal pattern in the serum samples suggests that this is not due to an alteration in the primary amino acid sequence. The lysosomal enzyme activities in serum and fibroblast extracts from the mucolipidosis III patients reported here are very similar to those found previously in mucolipidosis II (I-cell) patients. This suggests that the nature of the defect may be very similar in these two distinct disorders.