Test Directory

This test detects all major causes of the Prader-Willi and Angelman syndromes. Angelman syndrome (AS) (OMIM 105830) is characterized by severe developmental delay or intellectual disability, 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 the loss of paternal gene expression in the 15q11-q13 region. 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 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.

Specimen Type: Whole Blood

Alternate Specimen Type: LabCorp Buccal Swab

Collection Container: Lavender Top (EDTA)

Alternate Collection Container: Pale Yellow Top (ACD, Solution A) or LabCorp Buccal Swab Kit

Desired Specimen Volume: 7 mL whole blood or 4 buccal swabs

Whole Blood:

1. Collect 2 lavender top (EDTA) tubes via venipuncture.

Buccal Swab:

1. Collect buccal swabs utilizing the LabCorp Buccal Swab Kit.

Whole Blood:

1. Transport 7 mL of whole blood in the original collection containers.

Buccal Swab:

1. Submit buccal swabs using materials and instructions included with the LabCorp buccal swab kit. Maintain swabs at room temperature.

*Please provide pertinent findings, family or personal, of intellectual disability, autistic behaviors, developmental delay and obesity.

Please provide pertinent findings, family or personal, of intellectual disability, autistic behaviors, developmental delay and obesity.

Transport to the laboratory at room temperature.

• Frozen specimen
• Hemolysis
• Quantity not sufficient for analysis
• Improper container
• One buccal swab
• Wet buccal swab

 See patient report.

Approximately 11% of Angelman syndrome cases arising from UBE3A mutations will not be detected by this test.

• Angelman/PWS Methylation Assay
• Angelman and Prader-Willi Syndromes, DNA Analysis