Subacute necrotizing encephalopathy of Leigh type in a Yorkshire Terrier

Subacute necrotizing encephalopathy is a severe neurodegenerative disease characterized by necrosis of nerve tissue, especially in the brain. Clinical symptoms most often appear at a young age, appear suddenly and may be chronic, gradually worsening or episodic. Typical are epileptic seizures, behavioral changes, impaired consciousness, swallowing disorders, central blindness, impaired coordination of movement (ataxia), hypermetria (overshooting of movements), proprioceptive disorders, decreased sensitivity in the facial area, weakness of the limbs up to tetraparesis (paralysis of all limbs).

In Yorkshire Terriers, the disease is caused by the c.205_210delinsN[35] mutation in the SLC19A3 gene, which encodes the thiamine (vitamin B1) transporter and primarily ensures the uptake of this vitamin into the cells of the central nervous system.

The mode of inheritance of the mutation is autosomal recessive. It appears only in an individual who has inherited the mutated allele from both parents (recessive homozygous). A heterozygote is an individual who has received the mutated allele from only one of its parents, does not show any symptoms of the disease and is clinically healthy. However, it can pass the mutated allele to its offspring. In the case of mating two heterozygous individuals, theoretically 25% of the offspring will be completely healthy, 50% of the offspring will be carriers and 25% will inherit the mutated allele from both parents and will therefore be affected by the disease.

A genetic test can clearly reveal the genotype of the animal and is a suitable tool for breeders to prevent the unintentional reproduction of affected puppies.

.

Reference:

Drögemüller, M., Letko, A., Matiasek, K., Jagannathan, V., Corlazzoli, D., Rosati, M., Jurina, K., Medl, S., Gödde, T., Rupp, S., Fischer, A., Luján Feliu-Pascual, A., Drögemüller, C. : SLC19A3 loss-of-function variant in Yorkshire terriers with Leigh-like subacute necrotizing encephalopathy. Genes (Basel) 11:1215, 2020. Pubmed reference: 33081289