Use of a fluorescent analogue of galactocerebroside for assay of galactocerebroside beta-galactosidase activity in skin fibroblasts from patients with Krabbe's disease

A case of late variant form of infantile Krabbe disease with a partial deficiency of galactocerebrosidase

A female was diagnosed as a late variant form of infantile Krabbe disease at 1 year and 3 months because of the late onset of regressive clinical course, decreased motor nerve conduction velocities, high cerebrospinal protein concentration and partial deficiency of galactocerebrosidase (15.6%) in the cultured skin fibroblasts. She showed normal development until 8 months when she lost her ability of sitting alone after febrile infection, and died accidentally at 2 years and 4 months. A considerable residual enzyme activity may correlate to the milder clinical course of this case.

Biochemical aspects of globoid and metachromatic leukodystrophies

Galactosylceramides and sulfogalactosylceramides are characteristic lipids of the myelin sheath. Two genetically determined leukodystrophies are caused by an inability to enzymically hydrolyze these glycolipids. Thus, a deficiency of galactocerebroside beta-galactosidase results in globoid cell leukodystrophy, whereas a reduced activity of arylsulfatase A is responsible for metachromatic leukodystrophy. Besides these disorders, deficiencies of arylsulfatases A, B, C, and other sulfatases have been shown in a distinct condition called "multiple sulfatase deficiency." All of these disorders are fatal and are characterized by marked demyelination and severe mental retardation. The cause of this demyelination is not known. However, cytotoxic galactosylsphingosine and sulfogalactosylsphingosine have been suggested as the agents responsible for this demyelination. Recent immunological studies have also shown that patients with globoid and metachromatic leukodystrophies contain a mutant galactocerebroside beta-galactosidase and arylsulfatase A, respectively. The mutant enzymes have different kinetic properties compared to the enzymes from normal subjects. However, they can cross-react with antibodies to these enzymes. Since partially purified preparations of galactocerebroside beta-galactosidase and homogeneous arylsulfatase A are now available, the possibility of enzyme replacement therapy in globoid and metachromatic leukodystrophies is discussed.