Old English Sheepdogs and Gordon Setters suffer from a juvenile onset, autosomal recessive form of canine hereditary ataxia primarily affecting the Purkinje neuron of the cerebellar cortex. The clinical and histological characteristics are similar to hereditary ataxias in humans.

The cause of the disease has been identified, it is a mutation in the gene associated with the process of autophagy by which cell proteins and organelles are removed and recycled and its critical role in maintenance of the continued health of cells is becoming clear. The defect in the autophagy process results in neuronal death.

Clinical symptomps begins in juvenile to young adult dogs aged from six months to four years. Dogs develop pronounced hypermetria, a truncal sway and intention tremor, and signs progress to cause severe gait disturbances. Cerebellar atrophy can be identified by magnetic resonance imaging (MRI) and histopathological findings include loss of Purkinje cell, granule cell and molecular layer neurons causing atrophy of the cerebellar cortex. In more detailed work on Gordon Setters, profound changes in cerebellar neurotransmitter levels and synapses have been described, along with the development of Purkinje neuron axonal spheroids.