An interesting case of regenerative anaemia in a dog

Lucia Sanchini, DVM, MSc, Dip. ECVCP, FRCPath, MRCVS, EBVS Specialist in Veterinary Clinical Pathology. BattLab, UK.

SIGNALMENT AND HISTORY

A 10-year-old male Staffordshire Bull Terrier dog was presented to the referring vet with a few weeks’ history of listlessness and mild weight loss, despite eating regularly. The owner reported a couple of episodes of diarrhoea and sporadic vomiting, probably due to scavenging.

PHYSICAL EXAMINATION:

On clinical examination, the dog was bright and alert, with light pink mucous membrane and increased heart rate. The abdomen was slightly tense but non painful.

INVESTIGATIONS:

HAEMATOLOGY

Initial haematology results revealed moderate anaemia (HCT 0.24 L/L, reference intervals RI 0.37-0.55), microcytic (MCV 52.3 fL, RI 60-77), hypochromic (MCHC 26.7 g/dL, RI 32.0-39.0), with markedly increased reticulocytes (387.9 x 10^9/L, RI 0-60). Mild leucocytosis (23.17 x 10^9 /L, RI 6.0-15.0) with mild neutrophilia (18.63x 10^9/L, RI 3.0-11-.5) and mild toxic changes were also present, together with moderate thrombocytosis (831 x 10^9/L, RI 150-500). Biochemistry results revealed mild hypoalbuminemia and hyperglobulinaemia, a pattern often seen in inflammatory states. Given the lack of haematuria, haematochezia, melaena or history of recent surgery, the dog was discharged with a course of metronidazole for the sporadic diarrhoea and no further investigations were performed.

Three weeks later, the dog was presented again with further weight loss and increased weakness, and a second haematology profile was performed. HCT at that time was 0.13 L/L, and the anaemia was still regenerative with a reticulocyte count of 172.4 x 10^9/L. Mild leucocytosis and neutrophilia persisted, and moderate monocytosis (4.12 RI 0.00-1.40 x 10^9/L) was also present. Platelet count was still markedly increased (817 x 10^9/L).

Relevant blood smear findings are shown in picture 1

INTERPRETATION OF THE RESULTS

The haematology results revealed a microcytic hypochromic, regenerative anaemia. Regenerative anaemia is associated with blood loss and/or haemolysis. Given the lack of haematology and biochemistry alterations compatible with haemolysis (e.g. total bilirubin within normal limits, no spherocytes), the anaemia was considered due to blood loss. The patient was overall in good clinical conditions and no overt evidence of external blood loss was noted. This anaemia was therefore considered to be likely secondary to chronic GI blood loss and this was further supported by the presence of hypochromasia on the blood film, indicating some degree of iron deficiency, often seen in these cases. The presence of inflammatory leukogram, with toxic changes, raised globulin and thrombocytosis were supportive of inflammation.

Thrombocytosis is often seen as a reactive process, associated with the production of inflammatory cytokines (IL-6 and IL-11), and may accompany iron deficiency anaemia (but in this case the mechanism is unknown). Both differentials were considered likely in this case.

Abdominal ultrasound revealed a 2 cm mass in the jejunum, and multiple FNAs yielded moderate numbers of mesenchymal looking cells. They were mostly individualized and occasionally arranged in small rows associated with light pink extracellular material, on a slightly eosinophilic and viscous background. These cells appeared spindloid to stellate and have abundant light blue cytoplasm with poorly preserved cell borders. Nuclei were round to oval, with granular chromatin and small multiple round basophilic nucleoli. Anisocytosis and anisokaryosis were mild to moderate. The presence of a prevalent population of mesenchymal cells with mild to moderate atypia, together with the lack of inflammation and evidence of an abdominal mass, were overall considered supportive of mesenchymal neoplasia (sarcoma). Leiomyosarcoma and GIST (gastrointestinal stromal cell tumour) were considered the most likely differential diagnoses.

DIAGNOSIS

Jejunal mesenchymal neoplasia with chronic bleeding, leading to iron deficiency anaemia.

TREATMENT AND FOLLOW UP

The abdominal mass was removed, and histopathology confirmed a poorly differentiated leiomyosarcoma (vimentin-positive, desmin-positive, smooth muscle actin positive and c-kit negative). The dog recovered uneventfully, and the next haematology results revealed only mild inflammatory leukogram.

SUMMARY

Intestinal leiomyosarcomas usually present as solitary masses with slow growing rate and are often associated with chronic GI bleeding (due to ulceration of the mass). In this patient, the chronic blood loss led to iron deficiency anaemia, although a strong regenerative response was still present. This might be due to intermittent bleeding, which allowed enough time for a regenerative response, as seen in the first haematology report. However, with time, the decreased iron stores lowered the marrow response, as supported by the continuing but decreased reticulocytosis noted in the second haematology. With time if the source for blood loss persists, the anaemia is expected to become non regenerative, markedly microcytic and hypochromic. Iron deficiency states can be confirmed with measurement of serum iron and total iron binding capacity, whereas early stages can be detected measuring reticulocyte haemoglobin content. Examination of the blood smear could be helpful especially when microcytosis and hypochromasia are already marked.