Notable findings from a Norfolk terrier case study

The images (Figures 1 and 2; Wright-Giemsa 50×) and data (Table 1) are from an ethylenediamine tetra-acetic acid blood sample of an adult, male Norfolk terrier seen by the referring veterinarian for lethargy, anorexia and abdominal discomfort.

Based on the data and blood smear pictures provided, try to answer the following questions.

What is the most likely explanation for the leukocytosis observed?

Examination of the blood smear confirmed a mild leukocytosis. An increased number of neutrophils (blue arrows) and monocytes existed, and this was considered supportive of inflammation.

Abdominal ultrasound findings and increased 1,2-o-dilauryl-rac-glycero-3-glutaric acid-(6’-methylresorufin) ester (pancreatic specific) lipase values were supportive of pancreatitis, which was considered the likely cause for the inflammatory leukogram observed.

The mild, poorly regenerative anaemia seen was interpreted as anaemia of chronic disease. Both leukocytosis and anaemia resolved after treatment for pancreatitis.

What is the most likely cause for the thrombocytopenia?

The haematology results also showed a moderate thrombocytopenia confirmed on blood smear examination, as platelets were subjectively decreased in numbers and no clumps were visible at the feathered edge of the smear. Variable percentages of platelets were large (the same size as a red blood cell or larger) and were, therefore, referred to as giant platelets or macroplatelets.

Several differential diagnoses for genuine thrombocytopenia in dogs exist, including disseminated intravascular coagulation, which can accompany pancreatitis. This was ruled out as coagulation times and D-dimers were all within reference range. In the absence of other obvious causes for thrombocytopenia, a breed-related condition was considered likely.

Recently, an asymptomatic macrothrombocytopenia phenotypically similar to asymptomatic inherited macrothrombocytopenia in cavalier King Charles spaniels was described in a group of Norfolk terriers and associated with a point mutation in the β1-tubulin gene. Isolated cases were also reported in cairn terriers.