Bone marrow necrosis and myelophthisis: manifestations of T-cell lymphoma in a horse.

The research article details a rare case of T-cell lymphoma in a 14-year old American Paint horse and includes how the disease manifested in the horse leading to bone marrow necrosis and myelophthisis.

Background

• The horse was initially assessed due to mild colic, anorexia, fever, and pancytopenia, a condition where there’s a reduction in the number of red and white blood cells, and platelets.
• Physical checkup showed mild tachycardia (an abnormally fast heart rate), tachypnea (rapid breathing), and pale mucous membranes.

Medical Examination & Results

• Advanced tests showed hyperfibrinogenemia (elevated fibrinogen in the blood), and hyperglobulinemia (high level of globulins in the blood). Few unusual large cells were found in peripheral blood smears but tests for equine infectious anemia and antipenicillin antibody came out negative.
• Through serum protein electrophoresis, a polyclonal gammopathy was identified, indicating an abnormal increase in proteins in the blood made by the immune system.
• Bone marrow tests revealed unidentifiably hypercellular particles with obscured cellular detail. This led to the diagnosis of bone marrow necrosis, a clinical syndrome usually associated with malignant disorders.

Treatment & Outcome

• The horse was treated using antimicrobials, nonsteroidal anti-inflammatory drugs, and corticosteroids. The fever subsided but the pancytopenia worsened leading to petechiation (small, red or purple spots caused by bleeding) and epistaxis (bleeding from the nose).
• Due to the worsening health condition, the horse was humanely put to sleep. Postmortem studies revealed that the horse had a diffused round cell neoplasm or cancerous cell formation in several organs, including the bone marrow.
• Immunophenotyping identified the tumor cells as T-cell lineage, indicating T-cell lymphoma, a type of cancer that affects the T-cells. This cancerous infiltration in the bone marrow led to severe myelophthisis, a disorder characterized by the displacement of hemopoietic bone-marrow tissue either by fibrosis, tumors or cysts, and bone marrow necrosis.

Significance

• This study is significant as it reports the first known instance of lymphoma, specifically T-cell lymphoma, resulting in bone marrow necrosis in a horse. Additionally, it points out that the condition has been previously associated with lymphoma in humans and dogs.