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

Useful For

Preferred test to rule-out mucopolysaccharidosis IVA (Morquio A syndrome)


The test is not useful for establishing carrier status for Morquio A syndrome.

Reporting Name

N-Acetylgalactosamine 6 Slft, WBC

Specimen Type

Whole Blood ACD

Ordering Guidance

This test cannot be used to establish carrier status for Morquio A syndrome; sequencing of the GALNS gene is recommended. Order CGPH / Custom Gene Panel, Hereditary, Next-Generation Sequencing, Varies and specify Gene List ID: EMCP-JUFPRX.

Shipping Instructions

For optimal isolation of leukocytes, it is recommended the specimen arrive within 7 days of collection to be stabilized. Collect specimen Monday through Thursday only and not the day before a holiday. Specimen should be collected and packaged as close to shipping time as possible.

Specimen Required


Preferred: Yellow top (ACD solution B)

Acceptable: Yellow top (ACD solution A)

Specimen Volume: 6 mL

Collection Instructions: Send whole blood specimen in original tube. Do not aliquot.

Specimen Minimum Volume

5 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Whole Blood ACD Refrigerated (preferred) 7 days YELLOW TOP/ACD
  Ambient  7 days YELLOW TOP/ACD

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 (referred to as mucopolysaccharides [MPS] or glycosaminoglycans). Accumulation of MPS in lysosomes interferes with normal functioning of cells, tissues, and organs.


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 glycosaminoglycans, keratan and chondroitin sulfate, accumulate in multiple tissues but mainly bone, cartilage, heart valves, and cornea.  Clinical features and severity of symptoms of MPS IVA are widely variable affecting multiple body systems, in particular the skeletal system. Other clinical features may include 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 MPS IVA. Estimates of the incidence of MPS IVA 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 urinary levels of keratan sulfate and chondroitin-6-sulfate. Reduced or absent activity of N-acetylgalactosamine-6-sulfate sulfatase enzyme in leukocytes and/or fibroblasts can confirm the diagnosis. Sequencing of the GALNS gene (CGPH / Custom Gene Panel, Hereditary, Next-Generation Sequencing, Varies; specify Gene List ID: EMCP-JUFPRX) allows for detection of disease-causing variants in affected patients and identification of familial variants allows for testing of at-risk family members. Morquio B is a distinct disorder caused by a deficiency of beta-galactosidase and has a significant number of overlapping clinical features with MPS IVA. Enzyme analysis (BGAW / Beta-Galactosidase, Blood) is necessary to distinguish between the 2 types.

Reference Values

≥92 nmol/17 hour/mg protein


Very low enzyme activity levels are consistent with mucopolysaccharidosis IVA (Morquio A syndrome).

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. Sawamoto K, Alvarez Gonzalez JV, Piechnik M, et al. Mucopolysaccharidosis IVA: Diagnosis, treatment, and management. Int J Mol Sci. 2020 Feb 23;21(4):1517. doi: 10.3390/ijms21041517

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

Day(s) Performed

Preanalytical processing: Monday through Saturday

Assay performed: Once per month

Report Available

30 to 45 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 US Food and Drug Administration.

CPT Code Information


LOINC Code Information

Test ID Test Order Name Order LOINC Value
G6SW N-Acetylgalactosamine 6 Slft, WBC 24096-0


Result ID Test Result Name Result LOINC Value
62409 N-Acetylgalactosamine 6 Slft, WBC 24096-0
35778 Interpretation (G6SW) 59462-2
35777 Reviewed By 18771-6

Method Name



1. New York Clients-Informed consent is required. Document on the request form or electronic order that a copy is on file. The following documents are available:

-Informed Consent for Genetic Testing (T576)

-Informed Consent for Genetic Testing-Spanish (T826)

2. Biochemical Genetics Patient Information (T602)

3. If not ordering electronically, complete, print, and send a Biochemical Genetics Test Request (T798) with the specimen.

Testing Algorithm

For information see Lysosomal Storage Disorders Diagnostic Algorithm, Part 1

Mayo Clinic Laboratories | Genetics and Pharmacogenomics Catalog Additional Information: