Last update: 12/12/2007

Background to disease

OMIM # 313200

X-linked spinal and bulbar muscular atrophy (SBMA Kennedy syndrome) is an adult onset form of motor neurone disease characterised by proximal muscle weakness, atrophy and fasciculations. The course of disease is progressive and complicated by the involvement of the bulbar muscles. The disease may also be associated with signs of androgen insensitivity in affected males such as gynecomastia, reduced fertility and testicular atrophy.

SBMA was the first disorder in which the expansion of a trinucleotide repeat was described as the causative mutation; the disease is caused by expansion of a trinucleotide repeat (CAG) in the first exon of the androgen receptor gene on the X chromosome. Normal individuals have 9-36 CAG repeats. Patients with SBMA have 38-62 CAG repeats. Point mutations in the androgen receptor cause androgen insensitivity.

Laboratory Analysis

Analysis for this disease is now carried out by the Northern Genetics Laboratories under a reciprocal arrangement (GENLYNC). Please contact them directly regarding information regarding turnaround time and sensitivity. Local samples should still be sent via the Yorkshire Regional Genetic Laboratory where they will be forwarded as whole blood as appropriate. DNA from these samples can be stored in the Yorkshire Regional Genetic Laboratory if it is anticipated that future tests may be required (please indicate clearly on referral card if required).