1. Case Summary: by Emma Hooijberg Signalment and history Border Collie, neutered male, 2 years old generally healthy, used for agility, lives with 2 other dogs history of mild intermittent tonsillitis, improves after amoxicillin treatment developed small hernia and abscess post- castration, resolved

2. Signalment and history presented with history of intermittent decreased habitus and inappetance of 1 week duration. vomited once dog seen by referring vet, found to have fever (40.3C), treated with meloxicam and amoxicillin presented to outpatients clinic of university hospital as no improvement

3. Clinical examination body temp 39.3C, small mass in area of stomach/ cranial abdomen adominal ultrasound – non-obstructive gastric foreign body – 2 rubber toys removed via gastroscopy 2 days ago. dog treated with intravenous fluids and further amoxicillin fever continued for the first 4 days, last 2 days resolved without anti-inflammatory therapy, habitus and appetite good

4. Laboratory findings five blood samples taken over the last 6 days since presentation: WBC ranging from 0.7-1.4 x10 9 /L, initial downward trend, today improved from 0.7 x10 9 /L to 1.2 x10 9 /L. (RI 6.0-15.0) neutrophil count: 0.073-0.24 x10 9 /L, slight improvement last 2 days in blood smear: occasional segmented and band neuts, reactive lymphocytes, reactive monocytes thrombocyte count reduced (around 80 x10 9 /L)

5. mild normocytic normochromic anemia (Hct around 30%), no reticulocytes measured. Mild polychromasie, anisocytosis, schistocytosis and poikilocytosis on blood smear

6. bone marrow ( 2 days ago): hypercellular hyperplasia of megakaryocytes with increase in immature forms M:E ratio 4:1 myeloblasts 13%, promyel/myelocytes 40%, metam/band/segm 47% - ie left shifted rubriblasts 7%, pro/rubricytes 38%, metarubr 54% plasma cells 2% of ANC, although in some areas make up around 5-10% of the cells – ie focally increased macrophages, lymphocytes around 2% of ANC morphology of all cells normal In summary: severe peripheral leukopenia, bone marrow myeloid hyperplasia with left shift

7. Differential diagnoses acute and transient bone marrow injury Parvo? - Ag test negative, awaiting results of PCR idiosyncratic drug reaction? – meloxicam? rubber toys? other (none in history despite repeated enquiries) Border Collie related diseases Cobalamin deficiency – neutropenia not usually so severe, no dysplastic erythroid changes – awaiting serum cobalamin measurement Trapped Neutrophil Syndrome – usually experience problems when young, most euthanased < 1year. Unfortunately no previous blood samples. Considering genetic testing Cyclic hematopoiesis – not a grey Collie, too old Immune-mediated neutropenia (but all leukocytes plus thrombocytes low)

8. our questions! in the case of a bone marrow injury with apparent recovery based on the BM cytology, how long should it take for these myeloid cells to enter the blood and for the leukopenia to resolve? 2 days ago the bone marrow looked ready to explode with nice healthy helpful-looking neutrophils….are we too impatient? any other ideas, additions or comments on our DD list? since the dog is clinically doing well, the clinicians are in a patient mood, but there are whispers of prednisolone treatment if all tests come back negative

9. Answers received Leukocytes should normalized by 3-4 days AB-Testing difficult – however try steroids Give parenteral Cobalamin for a couple of days – WBC should turn to normal within a couple of days. Try flow-cytrometric detection of PLT autoantibodies;

10. Further Test results + Clinical course Cobalamin concentration WRI Gen-Test for Leukocyte-Trapping: negative Ab against Neutrophils: negative Waxing and waning course of TWBC and neutrophils; dog only on antibiotics – no steroids! Splenic mass was detected on US FNA: inconclusive, haematoma slight inflammatory infiltration

11. Splenectomy on 22nd of May because the mass seemed to grow Spontaneous increase of TWBC and Neutrophils on d1 post OP but then a new decline, but not as low as at the beginning See Graphs Histopathology of splenic mass: High grade splenic hyperaemia Hematoma in organisation No evidence of immune mediated disease

12. Splenectomy

15. Our Questions Could it be cyclic leukopoesis? Has the course of MPXI any meaning?