N-acetyl-alpha-glucosaminidase (Sanfilippo,
Type B; MPS IIIB)
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. There are four
enzymatically distinct forms of Sanfilippo syndrome with significant clinical
overlap. In all four types, urinary excretion of heparan sulfate is seen which
can be assessed via mucopolysaccharide
electrophoresis. Enzymatic testing is necessary to further distinguish
between the four types.
Sanfilippo, Type B is caused by a deficiency of
N-acetyl-alpha-D-glucosaminidase, one of four enzymes required for the
modification and removal of glucosamine residues from heparan sulfate. This
defect results in the accumulation of heparan sulfate in the patient’s cells and
organs which overtime leads to the clinical phenotype.
Molecular
testing for Sanfilippo, Type B is available. However, it is strongly
recommended that the enzymatic defect be identified in the proband before
molecular testing is performed.
Specimen requirements: Enzyme may be measured in
cultured fibroblasts or plasma.
Transport: Please contact the laboratory before
transporting tissue for enzyme assay. Fresh tissue for culture should be sent by
courier or 24-hour delivery. Plasma should be collected in a sodium heparin tube
and shipped overnight.
Standard of analysis: Assay will employ the
4-methylumbelliferyl substrate
Time required: Most assays will be complete in one
week; assays of cultured cells may take 3-4 weeks.
Special requests: Any type of special request must be
made directly with the laboratory.
Report: Written reports with interpretation are mailed
to the referring physician. Abnormal results will also be telephoned to the
referring physician.
CPT Code: 82657
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