Neuroaxonal dystrophy is an autosomal-recessive genetic disease of dogs characterized by neurodegenerative pathology of the central and/or peripheral nervous system.
In dogs, this condition appears as local swellings (spheroids) and atrophy of axons. This condition is caused by a mutation in the mitofusin 2 gene.
A neonate form manifests as fetal akinesia late in gestation and respiratory failure at birth, both due to lower motor neuron dysfunction, and is accompanied by cerebellar hypoplasia. Affected newborn pups usually present with acute respiratory distress, stereotypical positioning of limbs, scoliosis, arthrogryposis, pulmonary hypoplasia and respiratory failure.
Some dogs have delayed onset, with symptoms appearing in adult life or at old age with a slow-onset of neurological signs such as ataxia, intention tremors, hypermetria and laryngeal paralysis.
Postmortem examination usually reveals swollen axons/spheroids throughout thebrainstem, spinal cord and peripheral nerves. Cerebellar hypoplasia is a feature of this condition with degeneration of Purkinje cells and neurons prevalent throughout deep cerebellar nuclei. Segmental swellings of axons may also be evident with axonal swelling filled with membrane bound fragments filled with neurofilaments.
Immunohistochemical staining with alpha-synuclein in the dystrophic axons is a feature of this condition.
A differential diagnosis would include include cerebellar abiotrophy and ceroid lipofuscinosis as well as causes of peripheral neuropathy such as vitamin E deficiency, diabetes mellitus, normal aging, and exposure to certain toxins.
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