Test Catalog

Test ID: ANAS    
Alpha-N-Acetylglucosaminidase, Serum

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

Diagnosis of Sanfilippo syndrome type B (mucopolysaccharidoses type IIIB)


This test is not suitable for carrier detection.

Genetics Test Information Provides information that may help with selection of the correct genetic test or proper submission of the test request

This test is used for the diagnosis of mucopolysaccharidoses (MPS) IIIB (Sanfilippo Syndrome type B) only.


Sanfilippo types A, C, and D must be ruled out independently.

Testing Algorithm Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

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

The mucopolysaccharidoses (MPS) are a group of disorders caused by a deficiency of any of the enzymes involved in the stepwise degradation of dermatan sulfate, heparan sulfate, keratan sulfate, or chondroitin sulfate (glycosaminoglycans: GAG). Accumulation of GAG in lysosomes interferes with normal functioning of cells, tissues, and organs resulting in the clinical features observed in MPS disorders.


Sanfilippo syndrome (MPS type III) is an autosomal recessive MPS with 4 recognized types (A-D). Each type is caused by a deficiency in 1 of 4 enzymes involved in the degradation of heparan sulfate resulting in its lysosomal accumulation. Though biochemically different, the clinical presentation of all types is indistinguishable. Sanfilippo syndrome is characterized by severe central nervous system (CNS) degeneration, but other symptoms seen in MPS, such as coarse facial features and skeletal involvement, tend to be milder. Onset of clinical features usually occurs between 2 and 6 years in a child who previously appeared normal. The presenting symptoms are most commonly developmental delay and severe behavioral problems. Severe neurologic degeneration occurs in most patients by 6 to 10 years of age, accompanied by a rapid deterioration of social and adaptive skills. Death generally occurs by age 20, although individuals with an attenuated phenotype may have a longer life expectancy and remain functional into their third and fourth decades.


Sanfilippo syndrome type B is due to a deficiency of the enzyme N-acetyl-alpha-D-glucosaminidase (alpha-hexosaminidase), caused by variants in the NAGLU gene. Affected individuals demonstrate elevations of heparan sulfate in blood and urine (MPSBS / Mucopolysaccharidosis, Blood Spot and MPSQU/ Mucopolysaccharides Quantitative, Random, Urine). Diagnostic sequencing of the NAGLU gene (MP3BZ / Mucopolysaccharidosis IIIB, Full Gene Analysis, Varies) and deletion/duplication studies are available for patients with an enzyme deficiency.


Elevations in serum of alpha-N-acetylglucosaminidase and other hydrolases may be seen in patients with mucolipidosis II/III (I-cell disease).(1) I-cell disease is an autosomal recessive lysosomal storage disorder resulting in impaired transport and phosphorylation of newly synthesized lysosomal proteins to the lysosome due to deficiency of N-acetylglucosamine 1-phosphotransferase (GlcNAc). Characteristic clinical features include short stature, skeletal and cardiac abnormalities, and developmental delay. Measurement of alpha-N-acetylglucosaminidase activity is not the preferred diagnostic test for I-cell disease but may be included in the testing strategy.

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.

0.09-0.58 U/L

Interpretation Provides information to assist in interpretation of the test results

Deficiency of alpha-N-acetylglucosaminidase is diagnostic for Sanfilippo syndrome type B.

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

This assay detects Sanfilippo syndrome type B only. The 3 other types of Sanfilippo syndrome (A, C, and D) must be ruled out independently.


This assay will not identify carrier status for Sanfilippo syndrome type B.

Clinical Reference Recommendations for in-depth reading of a clinical nature

1. Braulke T, Raas-Rothschild A, Kornfeld S: I-cell disease and pseudo-Hurler polydystrophy: Disorders of lysosomal enzyme phosphorylation and localization. In: Valle DL, Antonarakis S, Ballabio A, Beaudet AL, Mitchell GA, eds: The Online Metabolic and Molecular Bases of Inherited Disease. McGraw-Hill; 2019. Accessed May 24, 2021. Available at https://ommbid.mhmedical.com/content.aspx?bookid=2709&sectionid=225544648

2. Heron B, Mikaeloff Y, Froissart R, et al: Incidence and natural history of mucopolysaccharidosis type III in France and comparison with United Kingdom and Greece. Am J Med Genet A. 2011;155A(1):58-68. doi: 10.1002/ajmg.a.33779

3. Neufeld EF, Muenzer J: The mucopolysaccharidoses. In: Valle D, Beaudet AL, Vogelstein B, et al; eds. The Metabolic and Molecular Bases of Inherited Disease. McGraw-Hill; 2019. Accessed May 24, 2021. Available at https://ommbid.mhmedical.com/content.aspx?sectionid=225544161&bookid=2709

4. Valstar MJ, Bruggenwirth HT, Olmer R, et al: Mucopolysaccharidosis type IIIB may predominantly present with an attenuated clinical phenotype. J Inherit Metab Dis. 2010;33:759-767. doi: 10.1007/s10545-010-9199-y.

4. Beneto N, Vilageliu L, Grinberg D, Canals I: Sanfilippo syndrome: Molecular basis, disease models and therapeutic approaches. Int J Mol Sci. 2020;21(21):7819. doi: 10.3390/ijms21217819

Special Instructions Library of PDFs including pertinent information and forms related to the test