Mucopolysaccharidosis IIIB (MPS IIIB), Sanfilippo syndrome B : N-acetyl-alpha-D-glucosaminidase Enzyme Analysis

Test Information

 

This biochemical test is a quantitative measurement of N-acetyl-alpha-D-glucosaminidase enzyme activity and can be used as a 1st tier test for patients with a clinical suspicion of . Demonstration of deficient N-acetyl-alpha-D-glucosaminidase enzyme activity is considered the gold standard to confirm a diagnosis of Mucopolysaccharidosis IIIB (MPS IIIB), Sanfilippo syndrome B.

In addition, this assay can be used to clarify molecular findings in the NAGLU gene and to monitor patients undergoing treatment.

 

Turnaround Time

2 weeks

CPT Code(s)

82657

Cost

$200


Enzymes

N-acetyl-alpha-D-glucosaminidase

Clinical Information

Sanfilippo syndrome is characterized by progressive developmental delay and behavioral problems. These patients have fewer of the somatic concerns seen in other types of MPS disorders.

Sanfilippo syndrome is caused by a defect in one of four enzymes required for the modification and removal of glucosamine residues from heparan sulfate. A defect in one of these four enzymes (types A-D) results in the accumulation of heparan sulfate in the patient�s cells and organs which overtime leads to the clinical phenotype. Patients with Sanfilippo syndrome experience delayed development with a progressively deteriorating mental status. Behavior and sleep problems are common as well as coarse facial features and stiff joints. The four types of Sanfilippo syndrome (A-D) are clinically indistinguishable, thus enzyme testing is recommended as an initial diagnostic test.

Indications

There are four enzymatically distinct forms of Sanfilippo syndrome with significant clinical overlap. Enzymatic testing is necessary to further distinguish between the following four types. These four enzymes are required for the modification and removal of glucosamine residues from heparan sulfate. These defects result in the accumulation of heparan sulfate in the patient�s cells and organs which overtime leads to the clinical phenotype. Enzyme analysis for each type of Sanfilippo syndrome may be ordered individually or as a panel.

Methodology

4-methylumbelliferyl substrate

Specimen Requirements

Enzyme activity can be measured in plasma, cultured fibroblasts, or dried blood spots. For plasma, please send 5-10 ml of whole blood in a green top (sodium heparin) tube OR plasma can removed from spun down sample and sent frozen. For dried blood spot collection, a minimum of three circles need to be filled in. Each circle should contain one drop of blood (about 100 microliters). See the link below for additional sample collection and handling instructions.

Transport Instructions

Whole blood should be sent over overnight at ambient temperature. Plamsa can be removed once the sample has been drawn and sent frozen on dry ice. Do not freeze whole blood.

Cultured fibroblasts can be sent overnight at room temperature.

For a dried blood spot: When the sample has dried 3-4 hours, fold cover at score line, over sample, and tuck into flap. Samples should be placed in the mail within 24 hours of collection. Overnight shipping is preferred.

Have Questions Need Support?

Call our laboratory at 1-800-473-9411 or contact one of our Laboratory Genetic Counselors for assistance.
Robin Fletcher, MS, CGC
Kellie Walden, MS, CGC

Biochemical Testing, Enzyme Analysis, Individual Enzyme Assays
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