Acute myelomonocytic leukemia in a horse.

The research is about a case of acute myelomonocytic leukemia in a 7-year-old Quarter Horse stallion, characterized by hematologic abnormalities, secondary complications after surgical removal of an enterolith, unsuccessful treatment attempts, and eventual necropsy findings of neoplastic infiltration in various organs.

Details of the Clinical Presentation

• The study presents the case of a 7-year-old Quarter Horse stallion, first examined due to colic symptoms, which is common in horses and refers to abdominal discomfort.
• During this examination, the horse was found to have an enterolith, a hard calcified mass occurring in the intestine, which was surgically removed.
• Post-surgery, the horse encountered complications that included leukopenia, a decrease in the number of white blood cells, and thrombocytopenia, a decrease in platelets essential for blood clotting.
• Five months later, the horse was examined again for persistent peripheral edema, a condition causing swelling due to excess fluid trapped in body’s tissues, and for the repair of abdominal incisional hernia, which occurred due to the previous surgery.

Diagnosis and Treatment of Acute Myelomonocytic Leukemia

• In this later examination, acute myelomonocytic leukemia was diagnosed. This is a rare and aggressive form of leukemia characterized by overproduction of myelomonocytic cells, immature cells in the bone marrow that are precursors to white blood cells.
• Unsuccessful attempts were made to treat the horse with low-dose (noncytocidal) cytosine arabinoside, a chemotherapy medication commonly used against leukemia and lymphoma in humans.

Necropsy Findings

• A necropsy was conducted after the horse’s demise, uncovering neoplastic infiltration in various organs including the spleen, liver, lung, adrenal gland, testes, and eyes. Neoplastic infiltration refers to the spread of cancer cells into organs or tissues in the body.
• The researchers propose that the hematologic abnormalities observed before the full-onset of leukemia could indicate preleukemia or dysplasia, conditions whose presence can increase the risk of developing leukemia.