A new variant mucolipidosis: biochemical investigations on two siblings.

Biochemical studies are presented on two siblings with some features of Mucolipidosis III, but with distinctive clinical findings. Levels of beta-galatosidase, alpha-mannosidase, beta-glucuronidase, N-acetyl-beta-glucosaminidase and alpha-fucosidase found in serum from these patients ranged from 10 to 10 times higher than normal. The ratio of heat stable to heat labile serum isoenzymes of N-acetyl-beta-glucosaminidase is considerably greater than normal. An extremely low activity of beta-galactosidase was found in fibroblasts cultured from one patient. Levels of the remaining enzymes were in the low normal range. Similarly, beta-galactosidase levels were low in heart, kidney, liver, spleen and lung of one patient who died during the course of the study. Activities of the remaining enzymes were close to normal. No excessive excretion of mucopolysaccharide was noted, however, changes in distribution of several fractions were found. Mucopolysaccharide labeled with radioactive sulfate was degraded by cultured fibroblasts at a normal rate. In addition to clinical differences, the biochemical studies further demonstrate the uniqueness of these patients.