PKDef or Pyruvate kinase deficiency

By the Veterinary Doctor Nathalie Vidal- Terrier

 

A. What is the PKdef. and how does it work?

 

The PKDef (not to be confused with PKD that affects the kidney by renal cyst formation) is an autosomal recessive genetic disease.

Pyruvate kinase is an enzyme erythrocyte (redblood cell erythrocyte =) involved in glycolysis and in the protection of erythrocytes in the process of oxidative degradation of hemoglobin.

Its deficit therefore causes a breakdown of redblood cells but has no effect on their production, which is important in the evolution of the disease.

During the glycolysis (glucose metabolism),especially during anaerobic glycolysis (absence of oxygen – Embden-Meyerhof)are produced reducing systems within erythrocytes, the products of these reducing systems (NADH and NADPH reduced) are entirely dependent on the presence of pyruvate kinase, without it, these gear systems do not work.Reduced NADH and NADPH are involved in energy production within the erythrocyteby degradation of intra-erythrocyte glucose. When there is deficiency of pyruvate kinase, this metabolism is not done, the energy deficit that leads to results in the destruction of red blood cells. It is this destruction that causes anemia.

In this case, it is called regenerative chronicanemia since the production of red blood cells is not affected, as opposed toanemia arégénératives.

 

B. Small genetic reminders

 

The PKDef. is the result of a mutation.

Called “N”, the normal allele and”n” allele carrying the mutation.

  • A healthy individual will be homozygous”NN”
  • A carrier of the mutation and not individualpatient is heterozygous “Nn”
  • A sick individual is homozygous “nn”

First case scenario : when Mating an individual”NN” and another individual “NN”.

First generation or F1 we will have 100%”NN”.

So if the parents are tested, (what each breeder will do before the future litter, it is absolutely unnecessary to test the kittens as they cannot carry the “n”, that the parents did not have.

Second case scenario : when mating an individual”NN” and an individual “Nn”.

We will have 50% of “NN” and 50%”Nn”.

Heterozygous “Nn” does not show disease but will in turn pass the “n” allele to their offspring

Third case scenario : when mating an individual “Nn” and Individual”Nn”.

We will have in F1: 50% “Nn” 25%”NN” and 25% “nn”.

The percentage of cats with “Nn” and % of cats “nn” is quite important!

Fourth case scenario : when mating a “nn” and “nn” we will have 100% “nn” therefore 100% of sick cats which is perfectly possible because the disease as we will see later can occur later on in life giving ample sick individual to be used in reproduction this is not an utopia as we have cases that exist!

 

1.3 Symptoms

 

The PKDef therefore causes intermittent regenerative chronic hemolytic anemia (but regeneration is moderate compared to dogs, for example). The red blood cells varies depending on the individual,age, the rate of regeneration.

The symptoms are those of anemia unremarkable fact that the difficulty of diagnosis, they vary greatly from one individual to another, from a simple fatigue to death of the cat.

These non specificsymptoms are:

  • Fatigability uplethargy
  • Anemia
  • Exercise intolerance
  • Heart murmur
  • Pale mucous membranes
  • Diarrhea
  • Dysorexie (decrease orloss of appetite) so weight loss
  • More rarely but still serious, jaundice (liver failure). This may be accompanied by jaundice ascites therefore a swollen abdomen.

The onset of symptoms is highly variable age between 1 and 13 years, usually after 7-8 years

The prognosis is guided by:

  • The age of onset of symptoms (more severe in younger and older cats).
  • The severity of clinical signs (darkening liver disease prognosis).
  • The importance of anemia.

 

1.4 Treatment

 

There is no specific treatment.

Blood transfusion in the most serious cases of anemia are used, hence the need to know the blood of a cat with repeated transfusions.

Treatment is symptomatic (cardiac support,anti-diarrheal treatment etc …).

 

1.5 In practice

 

Let us be logical, test should be done on the kitten only if parents are carriers or untested.

If DNA parentage testing are performed and if the parents are negative, that is to say non-carriers or “NN”, it is illogical to test the kittens, to test would be a waste of money as it is certain that they will be negative.This is what is done with the Abyssinian: breeders and individuals who adopt a kitten understand it very well, it is the same for PKD, PRA, etc …

Don’t worry, we are not the only breed where problems of genetic origin recessive diseases arise. This problem occurs in all species and it is absolutely guaranteed that if the parents are not carriers tests are unnecessary. In these cases, the presentation of the tests of the parents is a sufficient guarantee(again if genetic parentage testing has been carried out)

In short, the key is to test all breeding that is far from being done at present.

With the emergence of new genetic tests and knowledge of previously unknown diseases, it is possible that the future may reserve us with more surprises.

 

1.6 Breeds most commonly affected

 

(This does not mean that other breeds don’t have it)

  • Abyssinian
  • Bengal
  • Sterret cats
  • Maine Coon
  • Norwegian
  • Egyptian
  • Savannah
  • Siberian
  • Singapura
  • Somali

 

In conclusion:

DO TEST ALL YOUR ENTIRE CATS!

• Do not select for reproduction only kittens tested negative or “nn” with the exception of specific lines to be saved!

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