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Angelman Syndrome - DNA Methylation

Angelman syndrome is associated with ataxia, seizures, absence of speech, hyperactivity, hypopigmentation, and severe mental retardation, and is caused by absence of the maternally-inherited criticial region of chromosome 15.

For diagnosis, DNA methylation study of the PWS/AS Critical Region is the recommended method. If the methylation pattern is characteristic of paternal inheritance, this is diagnostic for Angelman syndrome. Paternal inheritance of the PWS/AS critical region can be caused by deletions of the maternal allele, receiving two copies of chromosome 15 from the father (uniparental disomy) or defects in the imprinting process.

DNA methylation studies will detect ~78% of cases of Angelman syndrome. If the methylation test is positive, a FISH (fluorescence in situ hybridization) test can be used to distinguish between uniparental disomy and a deletion.

11% of individuals with a clinical diagnosis of Angelman syndrome will have an imprinting defect caused by mutations in the UBE3A gene. Individuals with a clinical diagnosis of Angelman but normal methylation studies should have DNA sequencing of the UBE3A gene.

Test Name: DNA Methylation study - Angelman syndrome
Test Code:
PWS-AS
Test Description:
Methylation-specific PCR assay of SNRPN alleles.
Synonyms:
methylation
Indication:
The test is indicated for an individual with some or all of the following:

-developmental delay/mental retardation
-seizures
-expressive speech impairment
-movement/balance disorder (ataxia)
-unique behavior including happy demeanor and excitability
-hand flapping
Related Tests: Fluorescence in situ hybridization (FISH) ONLY to R/O Angelman syndrome  
This test is used as a follow-up test to a positive Angelman DNA methylation study.

Clinical Links: Angelman Syndrome GeneReview
Availability:
Mon - Fri
Turnaround Time:
2 weeks
Methodology:
Methylation sensitive PCR
Reference Range:
Interpretive report provided
Requisition:
Consent Form:
Sample Requirements: Type
Whole blood: 1-3 mL in EDTA (purple top) or ACD (yellow top)
DNA: 5-20ug extracted DNA

Processing
Refrigerate blood samples which will not be immediately shipped.

Shipping
Room temperature via overnight shipping.
Samples Received:
Mon – Fri 8:00 am – 5:00 pm PST
Special Considerations:
Cost:
Please e-mail Lab Client Services (labclientservices@seattlechildrens.org) or call at 206-987-2617 with any billing questions
CPT Code:
Please e-mail Lab Client Services (labclientservices@seattlechildrens.org) or call at 206-987-2617 with any billing questions