LabPLUS is part of Auckland District Health Board
and provides medical laboratory testing
| Services |
MOLECULAR GENETICS TESTS - SPINAL AND BULBAR MUSCULAR ATROPHY |
| Background: X-linked spinal and bulbar muscular atrophy (SBMA, Kennedy disease) is an adult onset form of motor neurone disease. Since the abnormality is X-linked, males are affected with females being unaffected carriers. SBMA is characterised by progressive muscle weakness and atrophy, but affected males also may have gynaecomastia and reduced fertility, suggesting a defect in the androgen receptor function. Disease onset is usually in the fourth to fifth decade of life, and progression is slow. The human androgen receptor (AR) gene has been mapped to Xq11-12 and linkage has localised the SBMA gene defect to the same region. The mutation that causes SBMA is an expansion of the CAG-trinucleotide repeat located in exon 1 of the androgen receptor gene. The size of the CAGn in an affected individual is roughly twice that of a normal individual. Affected alleles have repeat sizes ranging from 36 to 62 repeats, with normal alleles ranging in size from 11 to 34 repeats. In general, there is a correlation between the CAGn repeat length and disease severity, with larger repeats present in individuals most severely affected. Expanded alleles can undergo alterations in length when transmitted to the next generation. Due to late onset of this disease, a test capable of providing a diagnosis during the asymptomatic stages, as well as during the symptomatic stages can be very useful. Analysis:
Blood: 3 x 4.0mL whole blood into EDTA tubes . Invert several times to mix. Forward within 24-48 hours at ambient temperature. Paediatric Samples: Minimum of 3mL whole blood in EDTA tubes. Prenatal Samples:
200 mg of tissue. Specimen must be snap frozen within one hour of collection. Send specimen frozen on dry ice. Paraffin blocks of tissue are also acceptable. The tissue sample should not have had prolonged immersion in formalin before embedding. NOTE:
6 weeks once patient sample/s is received. Cost of test: SBMA - $145.53 Note: Prices excludes GST (12.5%) and may change without notice. Please click on a link below to view information about another specific test.
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