Test Detail

Bilateral, progressive stromal corneal dystrophy of the Labrador retriever, caused by the accumulation of glycosaminoglycans in the corneal stroma. It appears between 4.5 and 6 years of age as diffuse corneal opacity with white-yellowish punctate opacities, without inflammation or pain, and causes progressive visual impairment. It is inherited in an autosomal recessive manner and is associated with a missense mutation in CHST6.

Affected breed: Labrador retriever. In the published British cohort the estimated allele frequency was 0.017, corresponding to a theoretical carrier rate of 3.3% and an affected rate of 0.028%. Limited data outside the United Kingdom.

- Test breeding dogs with the CHST6 test before mating
- Do not mate two carriers: 25% risk of affected homozygotes
- A carrier may be mated to a clear dog; test the offspring intended for breeding
- Progressively replace carriers with clear offspring without narrowing the gene pool
- Do not regard a CHST6-clear homozygote as free of other corneal dystrophies

Differential diagnosis with other corneal dystrophies (superficial, endothelial) and with chronic non-hereditary keratitis. Optical coherence tomography and in vivo confocal microscopy show multifocal hyperreflective regions and alterations in stromal reflectivity. Genetic testing identifies carriers before signs appear, which is key because onset is in adulthood.

1. Tetas Pont R, et al. A Carbohydrate Sulfotransferase-6 (CHST6) gene mutation is associated with Macular Corneal Dystrophy in Labrador Retrievers. Vet Ophthalmol 2016;19(6):488-92. PMID: 26585178
2. Busse C, et al. Phenotype of macular corneal dystrophy in Labrador Retrievers: a multicenter study. Vet Ophthalmol 2019;22(3):304-15. PMID: 30701649
3. OMIA:002071-9615 (LOC489707/CHST6). https://omia.org/OMIA002071/9615/