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Interpretive Handbook

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Test 62238 :
Oligosaccharidoses Screen, Fibroblasts

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Oligosaccharidoses are a group of autosomal recessively inherited lysosomal disorders of glycoprotein catabolism. There is no treatment available at this time for these disorders. Details about the different oligosaccharidoses detected by this screening test are provided in the Table.

 

Table. Conditions identifiable by method(1):

Disorder

Onset

Gene

Enzyme Deficiency

Worldwide Incidence

Alpha-mannosidosis

Infancy (severe, Type I)

Adult (mild, Type II)

Prenatal (severe, Type III)

MAN2B1

Alpha- mannosidase (alpha-Mann)

1:500,000

Phenotype: highly variable; "mild" Hurlerlike features, learning difficulties, hepatosplenomegaly, deafness, immune deficiency

Beta-mannosidosis

Infancy to adolescence

MANBA

Beta-mannosidase (beta-Mann)

<30 patients described

Phenotype: highly variable; learning difficulties, deafness, frequent infections

Alpha-fucosidosis

Infancy to early childhood

FUCA1

Alpha-fucosidase (alpha-Fuc)

<100 patients described

Phenotype: highly variable; psychomotor retardation, coarse facial features, growth delay; angiokertoma, elevated sweat chloride

Schindler disease

Infancy (severe, Type I; intermediate, Type III)

Adult (mild, Type II)

NAGA

Alpha-N-Acetyl-galactosaminidase

(alpha-NAcGal)

<30 patients described

Phenotype: highly variable; early onset neurodegenerative phenotype to late onset angiokeratoma to no symptoms (phenotype may be dependent on additional factors than just alpha-NAcGal deficiency

GM1 gangliosidosis (a sphingolipidosis)

Infancy (severe, Type I; intermediate, Type II)

Adult (mild, Type III)

GLB1

Beta-galactosidase (beta-Gal)

1:200,000

Phenotype: fetal hydrops/neonatal cardiomyopathy to early developmental delay/arrest, facial coarseness, hepatosplenomegaly, failure to thrive, to 2nd/3rd decade onset of ataxia, speech abnormalities leading to spinocerebellar degeneration and cognitive decline. Cherry-red spot in early onset variants

Mucopoly-saccharidosis type IVB (Morquio B)

Childhood

GLB1

Beta-galactosidase (beta-Gal)

<30 patients described

Phenotype: dwarfism with scoliosis and vertebral deformities noted between 1 and 4 years old and progressively worsening; typically no CNS involvement; keratan sulfate excretion in urine

Sialidosis (ML I)

Early adulthood (Type I)

Earlier for congenital, infantile, and juvenile forms (Type II)

NEU1

Alpha-neuraminidase (Neu)

<30 patients described

Phenotype: fetal hydrops to early developmental delay, coarse facial features, dysostosis multiplex and hepatosplenomegaly, to late onset cherry-red spot myoclonus syndrome

Galactosialidosis

Early infancy, late infancy or early adult

CTSA

Cathepsin A causing secondary deficiencies in beta-Gal and Neu

<30 patients described

Phenotype: highly variable from fetal hydrops, edema, coarse facial features, corneal clouding, cherry-red spot, dysostosis multiplex, hepatosplenomegaly, mental retardation to milder presentation with survival to adulthood

Mucolipidosis II-alpha/-beta (I-Cell)

Mucolipidosis III-alpha/-beta and III-gamma (Pseudo-Hurler Polydystrophy)

Early infancy; death usually by age 5-8

 

GNPTAB

N-acetylglucosaminyl-1-phosphotransferase deficiency causing secondary intracellular deficiency of multiple enzyme activities

1:300,000

Early childhood, may live well into adulthood

Phenotype: Hurlerlike, with ML II being more severe and including cardiomyopathy and coronary artery disease

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Useful For Suggests clinical disorders or settings where the test may be helpful

Screening for possible oligosaccharidoses

Interpretation Provides information to assist in interpretation of the test results

This is a screening test; not all oligosaccharidoses are detected. The resulting enzyme activities may be characteristic of a specific disorder; however, abnormal results require confirmation by additional biochemical or molecular genetic analysis.

 

When abnormal results are detected, a detailed interpretation is given, including an overview of results and significance, a correlation to available clinical information, elements of differential diagnosis, and recommendations for additional confirmatory studies (enzyme assay, molecular genetic analysis).

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

The test can give false-negative results, especially in older patients with mild clinical presentations. Patients with mild sialidosis are not reliably detected.

 

Additional biochemical or molecular genetic analysis is required to confirm a suspected diagnosis.

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.

An interpretive report will be provided.

Clinical References Provides recommendations for further in-depth reading of a clinical nature

Scriver's The Online Metabolic and Molecular Bases of Inherited Disease (OMMBID), Part 16. Edited by D Valle, A L Beaudet, B Volgestein, et al, McGraw-Hill Companies, Inc. Available from URL: http://www.ommbid.com/


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