Test Detail

Type B1 progressive retinal atrophy of the Miniature Schnauzer (photoreceptor dysplasia, pd): progressive degeneration of photoreceptors leading to blindness, with a normal ocular fundus until 10 months and advanced disease by around 3 years. The commercial test detects an intronic SNV in HIVEP3 strongly associated with the phenotype: it is a useful and robust linked marker, although it is probably not the causal variant. The most likely causal variant is a complex structural rearrangement of PPT1 (PPT1dci), very difficult to genotype routinely.

Affected breed: Miniature Schnauzer (the only documented breed, OMIA:001311). Population carrier frequencies: limited data.

- Test breeding animals with the HIVEP3 marker test before mating.
- Do not mate two carriers/homozygotes with each other: risk of affected offspring (recessive).
- A carrier can be mated with a free animal; test the offspring intended for breeding.
- Interpret the result as a linked marker (not as direct causality) and confirm with the laboratory the variant covered by the assay.
- Periodic ophthalmological examination of breeding animals, because other PRAs exist in the breed.

The Miniature Schnauzer may present several forms of PRA with similar ophthalmoscopic pictures. Confirmation requires a specific genetic test for the HIVEP3 mutation. Differentiate from other PRAs (prcd-PRA, other Type A forms) by age of onset and molecular test.

1. Kaukonen M et al. 2020, variante silenciadora putativa en un modelo canino de retinosis pigmentaria; PRA tipos 1 y 2 del Schnauzer miniatura (PMID 32150541)
2. Murgiano L et al. 2019, variante estructural compleja de PPT1 asociada a degeneración retiniana canina no sindrómica (PMID 30541930)
3. Aguirre GD et al. 2020, comentario de consenso sobre HIVEP3 vs PPT1 (PMID 33151924)
4. Parshall C et al. 1991, displasia de fotorreceptores del Schnauzer miniatura (herencia AR demostrada)
5. OMIA:001311 Displasia de fotorreceptores (PRA tipo 1/pd) del Schnauzer miniatura