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Test ID: I2SW Iduronate-2-sulfatase, Whole Blood

Useful For

Diagnosis of mucopolysaccharidosis II (MPS II, Hunter syndrome) in whole blood specimens

Reporting Name

Iduronate-2-sulfatase, B

Specimen Type

Whole blood


Necessary Information


Provide a reason for referral with each specimen.



Specimen Required


Collection Container/Tube:

Preferred: Lavender top (EDTA)

Acceptable: Yellow top (ACD)

Specimen Volume: 2 mL


Specimen Minimum Volume

0.5 mL

Specimen Stability Information

Specimen Type Temperature Time
Whole blood Ambient (preferred) 7 days
  Refrigerated  7 days

Clinical Information

The mucopolysaccharidoses are a group of disorders caused by the deficiency of any of the enzymes involved in the stepwise degradation of dermatan sulfate, heparan sulfate, keratan sulfate, or chondroitin sulfate, also known as glycosaminoglycans(GAGs). Accumulation of GAGs (previously called mucopolysaccharides) in the lysosomes interferes with normal functioning of cells, tissues, and organs. Mucopolysaccharidosis II (MPS II, Hunter syndrome) is an X-linked lysosomal storage disorder caused by the deficiency of iduronate sulfatase (IDS) enzyme and gives rise to the physical manifestations of the disease.

 

Clinical features and severity of symptoms are widely variable ranging from severe infantile onset disease to an attenuated form, which generally has a later onset with a milder clinical presentation. Symptoms may include coarse facies, short stature, enlarged liver and spleen, hoarse voice, stiff joints, cardiac disease, and profound neurologic involvement leading to developmental delays and regression. As an X-linked disorder, Hunter disease occurs primarily in males with an estimated incidence of 1 in 120,000 male births, although symptomatic carrier females have been reported. Treatment options include hematopoietic stem cell transplantation and enzyme replacement therapy.

 

A diagnostic workup in an individual with MPS II typically demonstrates elevated levels of urinary glycosaminoglycans and increased amounts of both dermatan and heparan sulfate. Reduced or absent activity of IDS can confirm a diagnosis of MPS II; however, enzymatic testing is not reliable to detect carriers. Molecular genetic testing of the IDS gene allows for detection of the disease-causing mutation in affected patients and subsequent carrier detection in female relatives. Currently, no clear genotype-phenotype correlations have been established.

Reference Values

≥1.5 nmol/h/mL

Interpretation

Specimens with results below 1.5 nmol/h/mL in properly submitted specimens are consistent with iduronate-2-sulfatase deficiency (mucopolysaccharidosis II: MPS II). If clinically indicated, consider further confirmation by molecular genetic analysis of the IDS gene. Please note that this enzyme's activity can also be reduced in multiple sulfatase deficiency.(1) If clinically indicated, consider biochemical genetic testing of other sulfatases or molecular genetic testing of the SUMF1 gene to exclude MSD.

 

Normal results (≥1.5 nmol/hour/mL) are not consistent with iduronate-2-sulfatase deficiency.

Clinical Reference

1. Multiple Sulfatase Deficiency. In The Online Metabolic and Molecular Bases of Inherited Disease. #272200. Edited by W Wang. Updated 07/21/2011. Available at: www.omim.org/entry/272200 2. Neufeld EF, Muenzer J: The mucopolysaccharidoses. Chapter 136 In The Metabolic Basis of Inherited Disease. Eighth edition. Edited by D Valle. AL Beaudet, B Vogelstein. New York, McGraw-Hill Book Company. Accessed 1/25/2017. Available at: www.ommbid.com 3. Scarpa M: Mucopolysaccharidosis Type II. In GeneReviews. Edited by RA Pagon, MP Adam, hh Ardinger, et al. University of Washington, Seattle; 2007 Nov 6. Accessed 1/24/17. Available at www.ncbi.nlm.nih.gov/books/NBK1274/

Day(s) and Time(s) Performed

Wednesday, morning

Analytic Time

8 days

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.

CPT Code Information

82657

LOINC Code Information

Test ID Test Order Name Order LOINC Value
I2SW Iduronate-2-sulfatase, B In Process

 

Result ID Test Result Name Result LOINC Value
61902 Iduronate-2-sulfatase, B In Process
35211 Reviewed By No LOINC Needed
35212 Interpretation (I2SW) 59462-2

Method Name

Fluorometric Enzyme Assay

Forms

1. New York Clients-Informed consent is required. Please document on the request form or electronic order that a copy is on file. An Informed Consent for Genetic Testing (T576) is available in Special Instructions.

2. Biochemical Genetics Patient Information (T602) in Special Instructions.

Mayo Medical Laboratories | Genetics and Pharmacogenomics Catalog Additional Information:

mml-biochemical