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Test ID: G6SW N-Acetylgalactosamine-6-Sulfatase, Leukocytes

Useful For

 Assisting in the diagnosis of Morquio A disease

Reporting Name

N-Acetylgalactosamine 6 Slft, WBC

Specimen Type

Whole Blood ACD


Specimen Required


For optimal isolation of leukocytes, it is recommended the specimen arrive within 96 hours of draw to be stabilized. Draw specimen Monday through Thursday only and not the day before a holiday. Specimen should be drawn and packaged as close to shipping time as possible.

 

Container/Tube:

Preferred: Yellow top (ACD solution B)

Acceptable: Yellow top (ACD solution A)

Specimen Volume: 6 mL

Collection Instructions: Do not transfer blood to other containers.


Specimen Minimum Volume

5 mL

Specimen Stability Information

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

Clinical Information

Mucopolysaccharidosis IVA, (MPS IVA, Morquio A syndrome) is an autosomal recessive mucopolysaccharidosis caused by reduced or absent N-acetylgalactosamine-6-sulfate sulfatase (GALNS) enzyme activity. 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 (glycosaminoglycans: GAGs). Accumulation of GAGs (previously called mucopolysaccharides) in lysosomes interferes with normal functioning of cells, tissues, and organs.

 

Clinical features and severity of symptoms of MPS IVA are widely variable and affect multiple body systems. Clinical features may include skeletal dysplasia, short stature, dental anomalies, corneal clouding, respiratory insufficiency, and cardiac disease. Intelligence is usually normal. Treatment options are mostly limited to symptom management, however, more recently available enzyme replacement therapy has shown to be effective in improving some function and quality of life for individuals with Morquio A. Estimates of the incidence of Morquio A syndrome range from 1 in 200,000 to 1 in 300,000 live births.

 

A diagnostic workup in an individual with MPS IVA typically demonstrates elevated levels of urinary GAGs and increased keratan sulfate and chondroitin-6-sulfate detected via quantitative and qualitative liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis of the specific sulfates. Morquio B is a genetically distinct disorder caused by a deficiency of beta-galactosidase and has a significant number of overlapping clinical features with Morquio A. Enzyme analysis is necessary to distinguish between the 2 types. Reduced or absent activity of N-acetylgalactosamine-6-sulfate sulfatase enzyme in leukocytes and/or fibroblasts can confirm a diagnosis of MPS IVA. Sequencing of the GALNS gene allows for detection of disease-causing mutations in affected patients and identification of familial mutations allows for testing of at-risk family members.

Reference Values

≥92 nmol/17 hour/mg protein

Interpretation

Very low enzyme activity levels are consistent with Morquio A disease.

Clinical Reference

1. Hendriksz CJ, Harmatz P, Beck M, et al: Review of clinical presentation and diagnosis of mucopolysaccharidosis IVA. Mol Genet Metab 2013 Sep-Oct;110(1-2):54-64. DOI: 10.1016/j.ymgme.2013.04.002

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 732

3. Haddley K: Elosulfase alfa. Drugs Today (Barc) 2014 Jul;50(7):475-483. DOI: 10.1358/dot.2014.50.7.2177904

 

 

 

 

 

 

 

 

 

 

                                                                                                                                                          

Day(s) and Time(s) Performed

Varies

Analytic Time

30 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
G6SW N-Acetylgalactosamine 6 Slft, WBC In Process

 

Result ID Test Result Name Result LOINC Value
62409 N-Acetylgalactosamine 6 Slft, WBC In Process
35778 Interpretation (G6SW) 59462-2
35777 Reviewed By No LOINC Needed

Method Name

Fluorometric

Forms

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.

Mayo Medical Laboratories | Genetics and Pharmacogenomics Catalog Additional Information:

mml-biochemical