The Genetic Workup

Question 1

General guidelines for genetic dx

Answer 1

• breed and/ or sex predisposition
• dx in related animals in pedigree
• characteristic age of onset
• characteristic clinical signs

Question 2

prerequisite for genetic workup

Answer 2

• characterization of the dx
• knowledge of the mode of inheritance
• accurate diagnoses of affected animals

Question 3

Characterization of the dx

Answer 3

• Clinical characterization: clinical signs, pathology, age of onset, natural history (how has dx been progressing genetically dx usually progressive degeneration)
• biochemical characterizatoin
• has the dx been seen before in the breed or another breed (seen in related animals?)
• similar dx in humans or other animals

Question 4

polycystic kidney and liver dx

Answer 4

example we saw in west hyland terror puppies;
- had micro cysts on kinder and liver plus large cysts on liver
-had unaffected parents and 4/6 pups affected (both males and females) so autosomal recessive mode of inheritance; breeder redid breeding and again had affected puppies (3/5 pups)
Autosomal recessive polycystic kidney and liver dx= ARPKD
- multiple cysts on kidney and liver
- kidney failure
- liver failure
- early onset (3-4 weeks start seeing sings, usually dead or euthanized by 16 weeks, this is fatal)
- also seen in Scottish terriers most likely bc same mutation bc basically are same breed

Question 5

immunodeficient corgis

Answer 5

• no palpable lymph nodes, no lympnodes at all, no thymus, early onset (typical sign of genetic dx) (12 weeks onset for the corgis)
• males affected from this mother and from males born to sister of mom of affected males therefore most likely x linked recessive
• this was a dennovo mutation that started with female a few generations back (ie just appeared in this female a few generations back no further back than that)

Question 6

immunodeficient corgis vs basets

Answer 6

looked at genes of immunodeficient corgis vs bassets and found different mutations but in same gene

Question 7

immunodeficiency summary

Answer 7

• primary (genetic) vs secondary (environmental, HIV/ AIDs/ malnutrition)
• poor-doer
• chronic infections (primary)
• one or multiple organ systems involved
• opportunistic agents cause dx
• treatment resistant (primary)
• X-linked severe combined immunodeficiency (SCID)

Question 8

Birman kittens born hairless

Answer 8

• kittens shouldn’t be born hairless
• all kittens in litter were effected; autosomal recessive since parents weren’t affected but weir all kittens are affected
• kittens had no thymus; wouldn’t have lived past 12-13 weeks when maternal antibodies wane
• bred queen multiple other times and ended up with about 1/4 of her total offspring being affected, sometimes they don’t read the book and get weird thing like a whole litter being affected

Question 9

Bull mastiff pups with neural crest defects

Answer 9

• 8/12 pups affected with various dxs all related to neural crest defects; this can be genetic but also a lot of things that can cause neural tube defect
• owner was feeding only raw liver which has a lot of vitamins A which lead to disruption in pathway leading to these defects

Question 10

Genetic dx summary

Answer 10

• all dx are genetic until proven otherwise
• some dx associated with desired traits (Scottish folds)
• most dogs presented are purebreds
• most cats are mixed making it hard to get familial info because people find cats in dumpsters

Question 11

scotish fold cats

Answer 11

can’t breed 2 with folded ears together because will get severe cartilage defects have to breed to normal cat and it is a dominant trait so will get 1/2 with folded and 1/2 with normal ears; double dose of dominant trait not always a good thing