Spinobulbar Muscular Atrophy (Kennedy Disease), Molecular Analysis, Varies
Use
Spinobulbar muscular atrophy (SBMA), also known as Kennedy disease, is characterized by progressive muscle weakness, atrophy, and fasciculations typically manifesting in the fourth or fifth decade of life. This condition is linked to androgen insensitivity, with affected patients often exhibiting gynecomastia, reduced fertility, and testicular atrophy. Due to its X-linked inheritance pattern, males generally express the disorder, while females are asymptomatic carriers. The disease is caused by an expansion of a CAG trinucleotide repeat in the AR gene. The number of repeats correlates with disease severity and onset age, with larger expansions associated with earlier onset and faster progression.
Special Instructions
Not provided.
Limitations
The test may not detect other mutations within the AR gene not related to CAG-repeat expansion. Predictive testing in asymptomatic children is not recommended. The presence of a CAG-repeat expansion must first be documented in an affected family member to confirm the molecular basis of the disease. Improper specimen handling could interfere with test results. DNA yield and quality are crucial factors; specimens not meeting these criteria may result in test cancellation.
New York Approved
Methodology
PCR-based (PCR)
Biomarkers
LOINC Codes
- 35359-9 - AR gene Mut Anl Bld/T
- 50397-9 - Mol dx interp Bld/T Ql
- 82939-0 - Genetic variant details Bld/T
- 69047-9 - Geneticist review
- 42349-1
- 31208-2 - Specimen source
- 18771-6 - Provider signing name
Result Turnaround Time
14-21 days
Related Documents
For more information, please review the documents below
Specimen
Whole Blood
Volume
3 mL
Minimum Volume
Not provided
Container
Lavender top (EDTA) or yellow top (ACD)
Collection Instructions
Invert several times to mix blood. Send whole blood specimen in original tube. Do not aliquot.
Patient Preparation
A previous bone marrow transplant from an allogenic donor will interfere with testing.
Storage Instructions
Ambient (preferred) 4 days/Refrigerated 4 days/Frozen 4 days
Causes for Rejection
All specimens will be evaluated by Mayo Clinic Laboratories for test suitability.
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | 4 days |
| Refrigerated | 4 days |
| Frozen | 4 days |