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Genetics Lab

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Pompe Disease Enzyme Assay

Pompe disease (glycogen storage disease type II) is an inherited disorder of glycogen metabolism and a lysosomal storage disease, caused by a deficiency of the enzyme alpha-glucosidase (also called GAA and acid-maltase). Individuals with Pompe disease are unable to use the glycogen stored in the lysosomes for energy, resulting in the progressive storage of glycogen in the heart, liver, and skeletal muscle.

Pompe disease can present in infancy with profound hypotonia, cardiomegaly and cardiomyopathy or later in childhood and adulthood with progressive muscle weakness and respiratory insufficiency.

Late onset Pompe disease presenting in the second to seventh decade of life can appear with muscle weakness in the upper and/or lower extremeties, muscle weakness in the trunk and shortness of breath after exercise.

Diagnosis for Pompe disease can be made by measuring GAA activity in lymphocytes, blood spots, or cultured fibroblasts. Deficient activity is diagnostic for Pompe disease. Transfusion within 1 week may cause ambiguous results in blood. Individuals who appear to have Pompe disease but who do not demonstrate a significant enzyme deficiency in blood should be followed up with testing in cultured skin fibroblasts or DNA sequencing. Individuals with indeterminate activity in blood should also be followed up with either enzyme testing in cultured fibroblasts or DNA sequencing.

Test Name: Pompe (alpha-glucosidase, acid maltase)
Test Code:
A GLU
Test Description:
Quantitative measure measurement of alpha-glucosidase in white blood cells, dried blood spots or cultured fibroblasts. Acarbose is used to inhibit other isoenzymes.
Synonyms:
acid maltase; alpha-glucosidase; GSD II
Indication:
This test is used to diagnose Pompe disease in a symptomatic individual of any age. This test is not appropriate for determining carrier status or for prenatal diagnosis.
Related Tests: Pompe Sequencing Analysis  
This test is used to provide additional information regarding diagnosed patients or as a secondary confirmation of diagnosis. Sequencing can also be used for carrier testing.

Pompe Known Mutation Analysis  
This test is used for carrier testing at-risk relatives and prenatal testing for confirmed carriers. Mutations must be known.

Clinical Links: Glycogen Storage Disease Type II (Pompe Disease) GeneReview
Availability:
Run weekly
Turnaround Time:
7-10 days
Methodology:
Enzymatic rate reaction
Reference Range:
Reference ranges accompany report
Requisition:
Consent Form:
Sample Requirements: Type
Whole blood: 6-10ml ACD (yellow) or heparin (green) tube. Do NOT use gel separator tubes.
Dried blood spot: Fill 3 spots on filter paper (newborn screening card)
Cultured Fibroblasts: 2 T-25 flasks
Skin biopsy: 2-4mm skin punch biopsy

Processing
Whole blood: Do not spin! Keep at room temp
Dried Blood Spots: Do not touch spots, let dry at room temp

Shipping
Ship overnight at room temp. Sample must be processed within 24 hrs of collection.
Ship fibroblasts/skin biopsy in appropriate cell culture/transport media
Samples Received:
Mon - Fri 8:00am - 5:00pm PST. For Thursday shipping please arrange for AM courier delivery.
Special Considerations:
If fresh skin biopsy is submitted, Fibroblast Cell Culture (CH-SKIN) must be ordered separately. Please call to discuss.
Cost:
Please e-mail Client Services or call at 206-987-2617 with any billing questions
CPT Code:
Please e-mail Client Services or call at 206-987-2617 with any billing questions