Inherited pyruvate kinase (PK) deficiency is an autosomal recessive disease and has been described in many canine breeds including Basenji, West Highland White Terrier (WHWT), Beagle and others. PK is an important enzyme in glycolytic pathway and its deficiency causes a severe hemolytic anemia due to premature destruction of PK deficient red cells. The carrier (heterozygous) dogs exhibits no clinical signs, but affected (homozygous) dogs may present clinicopathologic manifestations at few months to few years of age. These patients present regenerative anemia with marked reticulocytosis and consequently weakness and exercise intolerance, pale mucous membranes, tachycardia, systolic hearth murmurs and hepatosplenomegaly may be noted. Anemia and hepatic failure are the main causes of death between 1-5 years of age and experimental bone marrow transplantation was the only successful treatment reported in literature. Highly reticulocytosis with severe anemia and osteosclerosis in young dogs are suggestive of PK deficiency and it is diagnosed through DNA analysis. DNA tests are accurate to detect affect and carrier dogs for multiple breeds. PK deficiency anemia was suspected in a 19-month-old female WHWT dog with history of weakness since 1-month of age. The dog was taken to many clinicians in the past and several exams were made and revealed all the PK deficiency findings described above, but the dog was still being treated for many other diseases. At the time the patient was admitted at HCV-UFRGS the hematological analysis revealed a severe and highly regenerative anemia. The urinalysis and biochemical exams were normal, and the direct Coomb's test was negative. A blood sample for DNA test was sent to Penn Gen Testing Lab (University of Pennsylvania, PA, USA) and the PK deficiency was confirmed. The patient was treated symptomatically and an extended blood typing was done and it was positive for DEA 1, 3, 4, 5 and 7. Crossmatching was done with ten different canine donors, including three familiar animals and only DEA 4 positive dogs. All of the tests were 4+ incompatible, it could be explain by previous transfusions without crossmatching or blood typing, or another RBC antigen. A blood positive only for DEA 4 was done besides those results and a little 24h clinical improvement was noticed after that. Human intravenous immunoglobulin was given to minimize the effects of a possible immunomediated factor that could aggravate the disease, but there was no clinical change. The patient was euthanized since its clinical condition was getting worse.