Anemia is one of the most common clinical signs and abnormal laboratory test results in companion animals. Although acquired conditions such as infections, immune disorders, intoxications, blood loss and chronic organ failures represent the main causes of anemia, hereditary blood diseases leading to anemia are also important in clinical practice. Several hereditary erythrocyte defects have been reported in cats and a molecular basis of the erythrocyte pyruvate kinase defect has recently been determined.
Pyruvate kinase is a key regulatory enzyme in the metabolism of sugar. Its deficiency leads to a lack of energy production and thus, an instability of erythrocyte blood cells. This will then result in anemia. PK deficient cats typically have intermittent anemia. The age of onset is quite variable and may depend on environmental factors. The youngest affected cat diagnosed with anemia was 6 months of age and the oldest affected cat was 12 years old and was only found based on screening cats for PK deficiency.
The clinical signs due to anemia are quite variable. Some animals will develop severe lethargy, weakness, and inappetence, and thereby lose weight. Their mucous membranes will be pale. They may develop some abdominal enlargement due to an enlargement of the spleen (splenomegaly). A careful search for acquired diseases, such as infections (hemobartonellosis, FeLV, FIV, and FIP infections), toxins (drugs, onions), and immune mediated hemolytic anemia fails to identify a trigger. Some cats may appear to respond to treatment for hemobartonellosis and immune disease, however, affected cats have very low PK activity in red blood cells.
PK deficiency has been recognized in Abyssinians, Somalis and domestic shorthair cats. This is an autosomal recessive inherited disease where affected animals have two mutated genes and carriers that are asymptomatic have one mutant and one normal gene. Over the past year, we have been testing more than 60 Abyssinian and Somali cats and have identified a dozen affected as well as a dozen carrier animals. To our surprise, not only anemic cats were found to have PK deficiency, but also some apparently asymptomatic cats that might have earlier experienced some unexplained form of anemia and were now found to have this gene defect. PK deficient cats have been found from the east coast to the west coast and from the north to the south of the United States and this disease is likely not restricted to this continent. We recommend testing the following Abyssinian and Somali cats for PK deficiency:
Testing for PK deficiency is rather simple, requiring a small amount of EDTA anti-coagulated blood shipped by a two-day reliable service to the Josephine Deubler Genetic Disease Testing Laboratory along with a submission form. Your veterinarian will gladly assist you to obtain and ship the blood sample to our laboratory. As affected cats may be in need of a transfusion, it might be prudent to have your cat's blood typed. The same blood sample sent to test for PK deficiency could be used for a blood typing test. Submission forms can be provided or obtained from our web site:www.vet.upenn.edu/penngen. Unfortunately, earlier versions of the submission forms were missing the question about the breed, which is important in our analysis. All data will be kept strictly confidential. Results will be sent within three weeks of receipt of the samples. In addition to payment by check, we now also accept VISA and MasterCard.
Urs Giger, PD, Dr.med.vet., MS, FVH
Diplomate, ACVIM & ECVIM
Charlotte Newton Sheppard Professor
of Medicine and Medical Genetics
Chief, Section of Medical Genetics
School of Veterinary Medicine