Serum lysosomal hydrolases in cystic fibrosis

The activities of a number of lysosomal hydrolases were determined in sera from 100 patients with cystic fibrosis (CF), age 2–35 yr, and age-matched controls: β-hexosaminidase activity was significantly elevated ( p < 0.005) in CF patients from all age groups. α-Mannosidase activity was increased only in the older CF patients (> 13 yr). The following enzyme activities were not altered in CF serum: α-fucosidase, β-glucuronidase and acid phosphatase. The abnormal patterns of serum α-mannosidase and β-hexosaminidase in CF cannot be explained by pancreatic disease or undernutrition, since serum values of these hydrolases in patients with anorexia nervosa or acute pancreatitis were not altered. However, the altered activities of the α-mannosidase and β-hexosaminidase were proportional to the degree of pulmonary insufficiency in the CF group, indicating that these changes are probably a secondary consequence of the primary disease process. Except for β-hexosaminidase, because differences in the serum hydrolases in CF do not become apparent until the second decade of life, determinations of lysosomal enzyme activities in serum will probably be of little diagnostic value.