Galactosylceramide Beta-Galactosidase, Leukocytes
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Krabbe disease (globoid cell leukodystrophy) is an autosomal recessive disorder caused by a deficiency of galactosylceramide beta-galactosidase (GBG). A deficiency of this enzyme leads to an accumulation of galactosylceramide in globoid cells (multinucleated macrophages) causing severe demyelination throughout the brain. The toxic metabolite galactosylsphingosine (psychosine), an apoptotic compound, accumulates in oligodendrocytes and Schwann cells and contributes to disease pathogenicity.
Severely affected individuals typically present between 3 to 6 months of age with increasing irritability and sensitivity to stimuli. Rapid neurodegeneration follows with death usually occurring by age 2. There are later onset forms of the disease that are characterized by ataxia, vision loss, weakness, and psychomotor regression. The clinical course of Krabbe disease can be variable even within the same family. Treatment is mostly supportive, although hematopoietic stem cell transplantation has shown some success if treatment begins before neurologic damaged has occurred.
Krabbe disease is caused by mutations in the GALC gene located on 14q31. Over 60 mutations have been described to date. Molecular genetic analysis, including deletion/duplication analysis, is commercially available in the United States. Contact Mayo Medical Laboratories for recommendations or contact information for laboratories that offer this testing.
Diagnosis of Krabbe disease
Values below the reference range are consistent with a diagnosis of Krabbe disease.
The upper limit of normal may change with the specific activity of the substrate. Elevated values have no known clinical significance.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
Because of the wide range of enzymatic activities observed in carriers and noncarriers, this test is not recommended for carrier detection.
Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
21.5-59.2 mU/g of protein
Note: The upper limit of normal may change with the specific activity of the substrate. This is of no consequence since Krabbe patients are below the lower limit.
Clinical References Provides recommendations for further in-depth reading of a clinical nature
1. Wenger DA: Krabbe Disease. Available from http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=gene&part=krabbe Reviewed March 29, 2011
2. Enns GM, Steiner RD, Cowan TM: Lysosomal Disorders. In Pediatric Endocrinology and Inborn Errors of Metabolism. Edited by Sarafoglou K, Hoffman G, Roth KS, New York, McGraw- Hill Medical, 2009, p 744