Sorted By Test Name - Mayo Medical Laboratories

ANAS
8782
APGH
9003
Alpha-N-Acetylglucosaminidase, Serum
Clinical Information: The mucopolysaccharidoses (MPS) 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 (glycosaminoglycans or GAGs). Undegraded or partially
degraded GAGs (also called mucopolysaccharides) are stored in lysosomes and/or are excreted in urine.
Accumulation of GAGs in lysosomes interferes with normal functioning of cells, tissues, and organs
resulting in the clinical features observed in MPS disorders. Sanfilippo syndrome is a MPS with 4
recognized types (types A-D) caused by different enzyme deficiencies; the clinical presentation of all
types, however, is indistinguishable. Sanfilippo syndrome is characterized by severe central nervous
system (CNS) degeneration, but other symptoms seen in MPS, such as coarse facial features, tend to be
milder. Such disproportionate involvement of the CNS is unique among the MPS. 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 though individuals with an attenuated
phenotype may have a longer life expectancy. Although there is no cure for Sanfilippo syndrome, research
of therapies has included bone marrow transplantation, enzyme replacement, and gene replacement.
Sanfilippo syndrome type B is due to the absence of the enzyme N-acetyl-alpha-D-glucosaminidase
(alpha-hexosaminidase), caused by mutations in the NAGLU gene. Diagnostic sequencing of the NAGLU
coding region and deletion/duplication studies are available for patients with an enzyme deficiency. Refer
to www.genetests.org for a listing of laboratories currently offering this testing.
Useful For: Diagnosis of Sanfilippo syndrome type B (mucopolysaccharidoses type IIIB)
Interpretation: Deficiency of alpha-N-acetylglucosaminidase is diagnostic for Sanfilippo type B.
Reference Values:
0.09-0.58 U/L
Clinical References: 1. Heron B, Mikaeloff Y, Froissart R, et al: Incidence and natural history of
mucopolysaccharidosis type III in France and comparison with United Kindgom and Greece. Am J Med
Genet A 2011;155A(1):58-68 2. Neufeld EF, Muenzer J: The mucopolysaccharidoses. In The Metabolic
and Molecular Bases of Inherited Disease. 8th edition. Edited by CR Scriver, AL Beaudet, D Valle, et al.
New York, McGraw-Hill Book Company, 2001, pp 3421-3452 3. 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
Alpha-Subunit Pituitary Tumor Marker, Serum
Clinical Information: The 3 human pituitary glycoprotein hormones: luteinizing hormone (LH),
follicle-stimulating hormone (FSH), thyrotropin (TSH), and the placenta-derived chorionic gonadotropin
(hCG), are closely related tropic hormones. They signal through G-protein-coupled receptors, regulating
the hormonal activity of their respective endocrine target tissues. Each is composed of an alpha- and a
beta-subunit, coupled by strong noncovalent bonds.The alpha-subunits of all 4 hormones are essentially
identical (92 amino acids; molecular weight [MW] of the "naked" protein:10,205 Da), being transcribed
from the same gene and showing only variability in glycosylation (MW of the glycosylated
proteins:13,000-18,000 Da). The alpha-subunits are essential for receptor transactivation. By contrast, all
the different beta-subunits are transcribed from separate genes, show less homology, and convey the
receptor specificity of the dimeric hormones. Under physiological conditions, alpha- and beta-chain
synthesis and secretions are tightly coupled, and only small amounts of monomeric subunits are secreted.
However, under certain conditions, coordinated production of intact glycoprotein hormones may be
disturbed and disproportionate quantities of free alpha-subunits are secreted. In particular, some pituitary
adenomas may overproduce alpha-subunits. Although most commonly associated with gonadotroph- or
thyrotroph-derived tumors, alpha-subunit secretion has also been observed in corticotroph, lactotroph, and
somatotroph pituitary adenomas. Overall, depending on cell type and tumor size, between 5% to 30% of
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