Pyruvate Kinase Deficiency

Pyruvate kinase is an enzyme red blood cells depend on to produce energy. Without enough of it, red cells are fragile and are destroyed faster than the body replaces them. The result is haemolytic anaemia.

PKdef is autosomal recessive. A cat needs two copies of the mutation — one from each parent — to be affected. A cat with a single copy is a carrier: perfectly healthy, with no symptom of any kind, and able to pass the mutation to half of its kittens.

Affected cats become lethargic, lose appetite and weight, show pale gums and sometimes jaundice, and can need transfusions or long-term management during a crisis.

What makes it deceptive is the timing. Onset is variable — it can appear in a young cat or hold off for years — so a kitten can look flawless at the point of sale and become ill long after it has settled into its new home.

The mutation is established in the Maine Coon population. Because carriers show nothing at all, it cannot be bred away from by observation, by pedigree reputation, or by buying from a cattery that simply has not seen a case. Untested lines accumulate it quietly.

The arithmetic is unforgiving: mate two carriers and, on average, one kitten in four is affected and two in four are new carriers who will carry it onward.

We test every breeding cat and never breed carriers. When both parents are confirmed clear, it is not merely unlikely that a kitten is affected — it is genetically impossible, because there is no second copy for it to inherit.

The clearances come from Langford Vets at the University of Bristol and travel with your kitten. You can see a full report on our genetic testing page.