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

Background Erythrocytic pyruvate kinase ( PK ) deficiency, first documented in B asenjis, 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 B eagles and W est H ighland W hite 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 P ug and B eagle 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 WHWT s, 9% and 35% were homozygous (affected) and heterozygous, respectively, for the previously described mutation (mutant allele frequency 0.26). A PK ‐deficient C airn T errier had the same insertion mutation as the affected WHWT s. Of the selected group of 68 B eagles, 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 .