Paroxysmal dystonia-ataxia syndrome in Weimaraners

The syndrome combines the symptoms of dystonia (increased muscle contractions leading to abnormal posture, limb twisting and stiffness) and ataxia (movement coordination disorder) with hypermetria (overshooting movements). Symptoms occur in episodes that occur several times a day for 5 to 15 minutes, often in response to emotional arousal or physical activity, and may result in collapse. The age of onset of clinical symptoms is 3 to 7 months.

The cause of the syndrome is the c.831dup mutation in the TNR gene, encoding tenascin-R. This is a member of the tenascin family of extracellular matrix glycoproteins that are expressed in the nervous system.

The mode of inheritance of the mutation is autosomal recessive. This means that only individuals who inherit the mutated gene from both parents will develop the disease. Carriers of the mutated gene are clinically healthy but pass the mutation on to their offspring. In the case of a mating between two heterozygous individuals, theoretically 25% of the offspring will be completely healthy, 50% of the offspring will be carriers and 25% of the offspring will inherit the mutated gene from both parents and will therefore be affected by the disease.

The genetic test can clearly reveal the genotype of the animal and is a useful tool for breeders to prevent unintentional breeding of affected puppies.

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Reference:

Christen, M., Bongers, J., Mathis, D., Jagannathan, V., Quintana, R.G., Leeb, T. : ACADM frameshift variant in Cavalier King Charles Spaniels with medium-chain acyl-CoA dehydrogenase deficiency. Genes (Basel) 13, 2022. Pubmed reference: 36292732