Spinocerebellar degenerative disease with involvement of peripheral nerves and posterior columns of spinal cord. Characterised by progressive, clumsy ataxic gait. Mean age of onset is 10 years – presenting feature is gait instability and falling. Most develop pes cavus, claw toes, wasting of intrinsic muscles progresses to loss of strength in all lower limb muscles – trunk and upper limb affected late. Also loose proprioception and vibration sensation. Deep tendon reflexes are diminished or lost. Mean age of wheelchair use is about 20 years.