Sanfilippo Syndrome, Types A, B, C and
D (MPS IIIA, B, C and D), Enzyme Analysis
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 following four types:
Sanfilippo A (heparin sulfamidase deficiency),
Sanfilippo, Type B (N-acetyl-alpha-D-glucosaminidase deficiency), Sanfilippo C
(Acetyl CoA: glucosaminidase N acetyl transferase deficiency) and Sanfilippo D
(N acetyl glucosamine 6 sulfatase deficiency). 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.
Molecular testing for
Sanfilippo, Type A and
Sanfilippo, Type B
is available in our laboratory. However, it is strongly recommended that the
enzymatic defect be identified in the proband before molecular testing is
performed.
Specimen requirements:
Fibroblasts or a sodium heparin (green top) tube of peripheral blood. Leukocytes
are used for enzyme analysis for Sanfilippo A, C and D. Plasma is used for
enzyme analysis for Sanfilippo B. If ordering the panel, a sodium heparin (green
top) tube is acceptable from which the plasma can be pulled off for type B and
then leukocytes can be isolated for types A, C and D. Enzymes can also be
measured via fibroblasts for all four types.
Transport:
Please contact the laboratory before transporting tissue for enzyme assay. Fresh
tissue for culture should be sent by courier or 24-hour delivery. Blood should
be collected in a sodium heparin tube and shipped overnight.
Standard of analysis:
Assay will employ a 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:
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