Erythrocytic Pyruvate Kinase Mutations Causing Hemolytic Anemia, Osteosclerosis, and Secondary Hemochromatosis in Dogs

Abstract

Background Erythrocytic pyruvate kinase (PK) deficiency, first documented in Basenjis, is the most common inherited erythroenzymopathy in dogs. Objectives To report 3 new breed‐specific PK‐LR gene mutations and a retrospective survey of PK mutations in a small and selected group of Beagles and West Highland White Terriers (WHWT). Animals Labrador Retrievers (2 siblings, 5 unrelated), Pugs (2 siblings, 1 unrelated), Beagles (39 anemic, 29 other), WHWTs (22 anemic, 226 nonanemic), Cairn Terrier (n = 1). Methods Exons of the PK‐LR gene were sequenced from genomic DNA of young dogs (<2 years) with persistent highly regenerative hemolytic anemia. Results A nonsense mutation (c.799C>T) resulting in a premature stop codon was identified in anemic Labrador Retriever siblings that had osteosclerosis, high serum ferritin concentrations, and severe hepatic secondary hemochromatosis. Anemic Pug and Beagle revealed 2 different missense mutations (c.848T>C, c.994G>A, respectively) resulting in intolerable amino acid changes to protein structure and enzyme function. Breed‐specific mutation tests were developed. Among the biased group of 248 WHWTs, 9% and 35% were homozygous (affected) and heterozygous, respectively, for the previously described mutation (mutant allele frequency 0.26). A PK‐deficient Cairn Terrier had the same insertion mutation as the affected WHWTs. Of the selected group of 68 Beagles, 35% were PK‐deficient and 3% were carriers (0.37). Conclusions and Clinical Importance Erythrocytic PK deficiency is caused by different mutations in different dog breeds and causes chronic severe hemolytic anemia, hemosiderosis, and secondary hemochromatosis because of chronic hemolysis and, an as yet unexplained osteosclerosis. The newly developed breed‐specific mutation assays simplify the diagnosis of PK deficiency.

Erythrocyte pyruvate kinase deficiency in three West Highland white terriers in Ireland and the UK

“…As in previous reports, these WHWTs, initially presented with minimal clinical signs or only mild signs of exercise intolerance. The clinical findings of pale mucous membranes and hepatosplenomegaly were similar to previous reports [2,6,8,11,13-15]. Typically, review of the blood smear demonstrates evidence of enhanced erythropoiesis (polychromasia, nucleated RBCs) and echinocytes and other poikilocytes are not seen.…”

“…This report details erythrocyte PK-deficiency in three anaemic WHWTs from Ireland and the UK and demonstrates the presence of the same insertion mutation in the R-PK gene as previously reported in WHWTs in the USA [2,10]. As in previous reports, these WHWTs, initially presented with minimal clinical signs or only mild signs of exercise intolerance.…”

“…Because the mutations are different from breed to breed [2,11], the activity and stability of the PK enzyme is more or less affected. As a consequence the disease manifests with slightly varying degrees of severity between affected populations.…”

“…Blood samples collected in ethylenediaminetetraacetic acid (EDTA) were independently submitted from each dog to PennGen laboratories (School of Veterinary Medicine, University of Pennsylvania, Philadelphia) for DNA testing for the mutation previously described in WHWTs in the USA [2,10]. Amplification of genomic DNA from blood yields a single 117 base pair (bp) product for genotypically normal dogs, and a larger product of 123 bp for PK-deficient WHWTs resulting from a 6 bp insertion.…”

Missense mutation in PFKM associated with muscle-type phosphofructokinase deficiency in the Wachtelhund dog

“…Similarly, in cases of ivermectin hypersensitivity [22] or factor VII deficiency [23,24] a single disease-causing mutation is observed in the multi-drug resistance 1 ( MDR1 ) gene [25,26] and factor VII ( FVII ) gene, respectively, for several closely related breeds. Conversely, different breed-specific mutations in the same gene can cause a single disease; examples include pyruvate kinase (PK) deficiency, a common erythroenzymoptathy affecting Basenjis [27], West Highland White Terriers [28], and most recently demonstrated in Labrador, Pug, Beagles and Cairn Terrier breeds [29] as well as von Willebrand disease, which is caused by several distinct mutations in the vWF gene in many different breeds [30]. In this report, we characterized a group of Wachtelhunds that were clinicopathologically diagnosed with PFK deficiency, but did not possess the originally described PFKM nonsense mutation [9,12].…”