Applied Clinical Genetics Case Library
Case 1

Signalment & History
Signalment:
  • 14-week-old
  • Intact female
  • Presumed Yorkiepoo
History:
  • Rescue post CPV treatment. Routine preventative care post-CPV.
  • Current txs: vaccines and monthly parasite preventatives
Presenting Complaint
  • Owner interested in breed ancestry
Physical Exam
  • Underweight, but otherwise unremarkable
Yorkshire Terriers are often (but not always) genetically predisposed to:
    • Degenerative Myelopathy, DM
    • Hyperuricosuria and Hyperuricemia or Urolithiasis, HUU
    • Primary Lens Luxation
    • Progressive Retinal Atrophy, prcd
Poodles (Small) are often (but not always) genetically predisposed to:
    • Degenerative Myelopathy, DM
    • Neonatal Encephalopathy with Seizures, NEWS
    • Osteochondrodysplasia, Skeletal Dwarfism
    • Progressive Retinal Atrophy, prcd
    • Von Willebrand Disease Type I, Type I vWD
    • Chondrodystrophy and Intervertebral Disc Disease, CDDY/IVDD, Type I IVDD
    • GM2 Gangliosidosis
  • Progressive Retinal Atrophy (PRA)
  • Explaining the at-risk, notable, and clear results. Explaining that these are all in terms of statistical probability. A dog that is “at-risk” is at higher risk of getting the illness than a dog that is “clear”, but could very well not develop that disease even still. We will test for these conditions during the appointment.
  • Normal ALT: 17-115 U/L; Dx ALT: 18 U/L Confirmed low normal ALT.
  • Late-onset PRA diagnosed from PE and genetics report.
  • Bloodwork to be rechecked annually to keep updated baseline and monitor for elevation.
    • Note that should ALT levels increase, an ultrasound should be performed.
  • Discussed ways to help dog adapt to her waning vision such as keeping furniture in the same location and training her to understand verbal commands or to use scent markers. 
  • Discussed oral antioxidant therapy (i.e. OcuGlo) to help delay “toxic” cataract formation.
  • This dog should be monitored by an ophthalmologist as she ages.
  • The treatment is mostly the same.
    • Neither PRA can be treated, but dogs with late onset PRA offer a greater opportunity for training and management interventions before they go blind. OcuGlo supplementation.
  • PRA: Dogs with two copies of this recessive variant in the PRCD gene are considered at risk for developing Progressive Retinal Atrophy, Progressive Rod-Cone Degeneration, prcd. Progressive retinal atrophy (PRA) describes a group of non-painful inherited degenerative or dysplastic disorders of the photoreceptor cells of the retina that results in vision loss in dogs. While there are management recommendations, currently, there is no widespread treatment for progressive retinal atrophy. However, gene therapy is an evolving field.
  • ALT: The variant in the GPT gene is codominant. Dogs with at least one copy of the ‘A’ allele are likely to have lower ALT activity (‘low normal’) than dogs with zero copies of the ‘A’ allele (‘normal’). So slight elevations in ALT, which could indicate liver injury, can go undiagnosed with standard blood testing since ALT may remain within reference ranges despite liver damage in some individuals. Having one or two copies of the variant does not cause liver disease, and this test is not providing an ALT blood level result.