Test ID: FUCW
Alpha-Fucosidase, Leukocytes

Detection of fucosidosis

Unless fucosidosis is the only lysosomal storage disease being

considered, fibroblasts are preferred since they provide a long-

term source of all of the lysosomal enzymes.

Not recommended for carrier detection.

Fucosidosis is an autosomal recessive lysosomal storage disorder caused by reduced or absent alpha-L-fucosidase enzyme activity. This enzyme is involved in degrading asparagine-linked, fucose-containing macromolecules (oligosaccharides, glycoasparagines) present in cells. Reduced or absent activity of this enzyme results in the abnormal accumulation of these undigested molecules in the tissues and body fluids of fucosidosis patients. Although the disorder is panethnic, the majority of reported patients have been from Italy and southwestern United States. There are currently 77 described cases.

Severe and mild subgroups of fucosidosis, designated types I and II, have been described, although recent data suggests individual patients may represent a continuum within a wide spectrum of severity. The more severe type is characterized by infantile onset, rapid psychomotor regression, and severe neurologic deterioration. Additionally, dysostosis multiplex and elevated sweat sodium chloride are frequent findings. Death typically occurs within the first decade of life. Those with the milder phenotype express comparatively mild psychomotor and neurologic regression, radiologic signs of dysostosis multiplex, and skin lesions (angiokeratoma corporis diffusum). Normal sweat salinity, the presence of the skin lesions, and survival into adulthood most readily distinguish milder from more severe phenotypes.

 A diagnostic workup includes urine thin-layer chromatography (#84340 “Oligosaccharide Screen, Urine”), which may reveal the characteristic banding pattern associated with fucosidosis. In addition, enzyme assay of alpha-L-fucosidosis can confirm the diagnosis. Unless fucosidosis is the only lysosomal storage disease being considered, fibroblasts are preferred since they provide a long-term source of all of the lysosomal enzymes. Enzyme analysis should be pursued in cases with strong clinical suspicion regardless of the urine screening result. Molecular (DNA) analysis is not available in the United States at this time.

0.49-1.76 U/g of cellular protein

Low alpha-fucosidase suggests fucosidosis when accompanied with the clinical findings discussed above. Occasionally, values below the normal range occur. Since significant activity is present in those patients, these results do not suggest fucosidosis.

See "Lysosomal Storage Disorders" in Special Instructions for further information on lysosomal storage diseases.

Low alpha-fucosidase variants in serum have been shown in the absence of fucosidosis. Though this has been associated with ovarian cancer, it is not a consistent finding and makes serum testing for fucosidosis unreliable.

This leukocyte test is not appropriate if lysosomal storage diseases other than fucosidosis are being considered. In that situation, order #8815 "Alpha-Fucosidase, Fibroblasts"; fibroblasts are preferred since they provide a long-term source of all of the lysosomal enzymes

The current laboratory procedure is for disease testing only. Carrier status detection by this method is not possible as normal individuals may exhibit rather low levels of alpha-fucosidase activity.

1. Cowan TM, Yu C: Laboratory Investigations of Inborn Errors of Metabolism. In Pediatric Endocrinology and Inborn Errors of Metabolism. Edited by K Sarafoglou, GF Hoffmann, KS Roth, New York, McGraw-Hill Medical Division, 2009, pp 867-868

2. Enns GM, Steiner RD, Cowan TM: Lysosomal Disorders. In Pediatric Endocrinology and Inborn Errors of Metabolism. Edited by K Sarafoglou, GF Hoffmann, KS Roth, New York, McGraw-Hill Medical Division, 2009, pp 747-748

3. Thomas, GH: Disorders of Glycoprotein Degradation: alpha-Mannosidosis, beta-Mannosidosis, Fucosidosis, and Sialidosis. In Scriver’s The Online Metabolic and Molecular Basis of Inherited Disease (OMBBID) Edited by Valle D, et al, The McGraw-Hill Companies, Inc

• Lysosomal Storage Disorders
• Informed Consent for Genetic Testing