Spinal and bulbar muscular atrophy: pathogenesis and clinical management.

Spinal and bulbar muscular atrophy, or Kennedy's disease, is an X-linked motor neuron disease caused by polyglutamine repeat expansion in the androgen receptor. The disease is characterised by weakness, atrophy and fasciculations in the limb and bulbar muscles. Affected males may have signs of androgen insensitivity, such as gynaecomastia and reduced fertility. Neurophysiological studies are typically consistent with diffuse denervation atrophy, and serum creatine kinase is usually elevated 2-5 times above normal. Progression of the disease is slow, and the focus of spinal and bulbar muscular atrophy (SBMA) management is to prevent complications.