Diagnostic and predictive testing for juvenile polyposis syndrome (JPS) or JPS/hereditary hemorrhagic telangiectasia.
- Patient Preparation
- Lavender (EDTA), pink (K2EDTA), or yellow (ACD Solution A or B).
- Specimen Preparation
- Transport 3 mL whole blood. (Min: 1 mL)
- Storage/Transport Temperature
- Unacceptable Conditions
- Ambient: 72 hours; Refrigerated: 1 week; Frozen: Unacceptable
Characteristics of Juvenile Polyposis Syndrome (JPS): Gastrointestinal (GI) bleeding, multiple hamartomatous polyps in the GI tract, increased risk for GI carcinoma.
Characteristics of JP/Hereditary Hemorrhagic Telangiectasia (HHT): Recurrent nosebleeds, telangiectases (mouth, face, hands, GI tract), arteriovenous malformations (lung, brain, liver, spine) and hamartomatous polyps in the GI tract.
Incidence: 1 in 16,000 to 1 in 100,000 for JPS; unknown for JP/HHT.
Inheritance: Autosomal dominant; de novo mutations occur in 25 percent of JPS.
Penetrance: Suspected to be greater than 90 percent for JPS.
Cause for JPS: Mutations in SMAD4, BMPR1A, and other unknown genes.
Cause for JP/HHT: Mutations in SMAD4.
Clinical Sensitivity: Approximately 20 percent for JPS; unknown for JP/HHT.
Methodology: Bidirectional sequencing of the entire coding region and intron/exon boundaries of the SMAD4 gene.
Analytical Sensitivity and Specificity: 99 percent.
Limitations: Diagnostic errors can occur due to rare sequence variations. Regulatory region mutations, deep intronic mutations, and large deletion/duplications will not be detected. Mutations in genes other than SMAD4 will not be detected.
Counseling and informed consent are recommended for genetic testing. Consent forms are available online.
|Component Test Code*||Component Chart Name||LOINC|
|0051509||Juvenile Polyposis (SMAD4) Sequencing|
|2001377||SMAD4 SEQ Specimen|
- SMAD4 sequencing