Sensory Ataxic Neuropathy

Sensory neuropathy in dogs is a progressive neurological disease that affects the sensitivity of the animal's limbs. This pathology can affect golden retriever dogs and is caused by a mutation in the mitochondrial DNA.

Symptoms

The first symptoms usually appear between two and seven months of age and include ataxia, abnormal gait, joint laxity and mild muscle atrophy that does not appear to be painful. As the pathology progresses, urinary incontinence may occur and dogs lose sensation in all limbs and are unable to recognize the position of their paws in space. When they completely lose sensation in their paws, they often bite them, resulting in severe wounds.

Disease Management

Although there is no cure for sensory neuropathy in golden retrievers, measures can be taken to manage the symptoms and improve the dog's quality of life. These may include physical therapy and other supportive treatments. In most cases, however, euthanasia is resorted to when the animal's quality of life worsens markedly.

Genetic basis

This disease follows a mitochondrial mode of inheritance. Unlike nuclear DNA, DNA can be found in the mitochondria of cells. Mitochondria are small intracellular compartments that produce energy in the cell and each mitochondrion contains its mtDNA. Therefore, within a cell there are multiple mitochondria and multiple copies of mtDNA. The mtDNA in dogs, as in humans, is only inherited from the mothers. For a dog to be at risk for a disorder that follows a mitochondrial mode of inheritance, it must inherit a certain proportion of mtDNA with the mutation or gene variant compared to normal mtDNA. The symptoms of the mitochondrial disorder depend on the mutation and the proportion of mutated mtDNA to the total mtDNA in the cell. In general, the more mutated mtDNA in a cell, the more symptoms the individual will have. There may be several affected puppies in the same litter with the mitochondrial disorder and with varying symptomatology.

Technical report

Sensory neuropathy in golden retriever dogs is a disease that manifests with loss of coordination, joint laxity, loss of proprioception, and inability to perceive pain. Merveille et al. identified the disease-causing mutation (m.5304del) in the mitochondrial MTTY gene (also called tRNA-Tyr gene) that encodes for the amino acid tyrosine transfer RNA. Since this gene is located in the mitochondrial DNA, the mutation is transmitted from females.

Most affected breeds

Golden Retriever

Bibliography

Jäderlund KH, Orvind E, Johnsson E,et al. A neurologic syndrome in Golden Retrievers presenting as a sensory ataxic neuropathy. J Vet Intern Med. 2007 Nov-Dec;21(6):1307-15.

Merveille AC, Davis EE, Becker-Heck A,et al. CCDC39 is required for assembly of inner dynein arms and the dynein regulatory complex and for normal ciliary motility in humans and dogs. Nat Genet. 2011 Jan;43(1):72-8.