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ANGELMAN/PWS METHYLATION ASSAY
MessageLabCorp
Test Code
511210
Alias/See Also
"Prader-Willi and Angelman Syndromes, DNA Analysis
PWS Methylation Assay
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PWS Methylation Assay
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CPT Codes
88230; 88262; 88289
Preferred Specimen
"Whole blood, amniotic fluid, or LabCorp buccal swab kit (buccal swab collection kit contains instructions for use of a buccal swab). Note: Submission of maternal blood is required for fetal testing.
7 mL whole blood, 10 mL amniotic fluid, or LabCorp bucc
7 mL whole blood, 10 mL amniotic fluid, or LabCorp bucc
Minimum Volume
"3 mL whole blood, 5 mL amniotic fluid, or two buccal swabs
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Transport Container
"Lavender-top (EDTA) tube, yellow-top (ACD) tube, sterile plastic conical tube or two confluent T25 flasks for fetal testing, or LabCorp buccal swab kit
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Transport Temperature
Refrigerated
Specimen Stability
"Maintain specimen at room temperature or refrigerate. Do not freeze
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Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
"Frozen specimen; hemolysis; quantity not sufficient for analysis; improper container; one buccal swab; wet buccal swab
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Methodology
"Methylation-specific PCR and gel electrophoresis "
Limitations
"Approximately 11% of Angelman syndrome cases arising from UBE3A mutations will not be detected by this test.
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Clinical Significance
"This test detects all major causes of the Prader-Willi and Angelman syndrome
Angelman syndrome (AS) (OMIM 105830) is characterized by severe developmental delay or mental retardation, severe speech impairment, gait ataxia and/or jerking limb motions, and an inappropriate happy demeanor that includes frequent laughing, smiling, and excitability. Neonatal hypotonicity may also occur. Approximately 70% of AS patients have a deletion of 15q11-13 in the maternally-contributed chromosome 15, with about 3% to 5% of AS cases resulting from paternal uniparental disomy (UPD). Approximately 11% of AS cases result from mutations in the maternal copy of the UBE3A gene that also maps to 15q11-13. An abnormality of the imprinting process occurs in a portion of the remaining patients.
Prader-Willi syndrome (PWS) (OMIM 176270) is caused by an abscess of paternal SNRPN gene expression. The disease is characterized by diminished fetal activity, severe postnatal hypotonia, failure to thrive in infancy followed by hyperphagia, obesity, developmental delay, and hypogonadism. PWS may result from a microdeletion of the paternal chromosome at 15q11-13 (70%), maternal UPD (25%), or from an imprinting defect.
Imprinting defects may be associated with a 50% recurrence risk, however, the risk is negligible for cases involving microdeletions or UPD. Consequently, etiological testing may be indicated. All test results must be combined with clinical information for the most accurate interpretation.
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Angelman syndrome (AS) (OMIM 105830) is characterized by severe developmental delay or mental retardation, severe speech impairment, gait ataxia and/or jerking limb motions, and an inappropriate happy demeanor that includes frequent laughing, smiling, and excitability. Neonatal hypotonicity may also occur. Approximately 70% of AS patients have a deletion of 15q11-13 in the maternally-contributed chromosome 15, with about 3% to 5% of AS cases resulting from paternal uniparental disomy (UPD). Approximately 11% of AS cases result from mutations in the maternal copy of the UBE3A gene that also maps to 15q11-13. An abnormality of the imprinting process occurs in a portion of the remaining patients.
Prader-Willi syndrome (PWS) (OMIM 176270) is caused by an abscess of paternal SNRPN gene expression. The disease is characterized by diminished fetal activity, severe postnatal hypotonia, failure to thrive in infancy followed by hyperphagia, obesity, developmental delay, and hypogonadism. PWS may result from a microdeletion of the paternal chromosome at 15q11-13 (70%), maternal UPD (25%), or from an imprinting defect.
Imprinting defects may be associated with a 50% recurrence risk, however, the risk is negligible for cases involving microdeletions or UPD. Consequently, etiological testing may be indicated. All test results must be combined with clinical information for the most accurate interpretation.
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