Myelomonocytic myeloproliferative diseases in a horse.

The research article details a case of Myelomonocytic myeloproliferative disease in a horse, highlighting the symptoms, diagnostic findings, and eventual death of the animal. The disease was determined through various tests including hematologic, enzymatic, and histopathologic evaluations.

Clinical Signs and Hematologic Findings

• The horse exhibited noticeable signs of depression and weight loss as well as observable physical abnormalities such as enlarged spleen (splenomegaly), enlarged lymph nodes (lymphadenopathy) and clotting disorders (coagulopathy). It was also found to have bacteria in its blood (bacteremia).
• Hematologic findings revealed severe unresponsive anemia, a decrease in the number of platelets (thrombocytopenia), an increase in monocytic white blood cells (monocytosis), and a variety of shapes and sizes in leukocytes, typically indicating an immune response to infection or disease. There was a marked rise in the number of immature white blood cells, namely in the myeloid series (cells that give rise to granulocytes and monocytes).

Enzymatic and Histopathologic Findings

• The serum lysozyme concentration, an enzyme that can break down bacterial cell walls, was significantly higher than the normal level. This could be an indicator of bacterial infection or a reaction to inflammation caused by the disease.
• The bone marrow had an unusual amount of immature myeloid series cells leading to an imbalanced myeloid-to-erythroid ratio (30.5:1) when the normal ratio is closer to 1:1 or 3:1. This phenomenon strongly suggested proliferation of myeloid cells.
• The autopsy showed generalized lymphadenopathy, which is a condition where the lymph nodes throughout the body are abnormal in size, number or consistency. Also, hemorrhages were found throughout the body, indicating severe bleeding.
• Microscopic examination of various tissues revealed presence of immature cells. Cells proliferating in the bone marrow were mainly myeloblastic, with some erythropoietic cells. These cells were also observed in numerous lymph nodes and in the spleen. The predominant cells in the lungs, myocardium, liver, and kidneys were of the myeloid blast-type.