Rapid clinical progression of B-cell chronic lymphocytic leukemia in a horse.
Abstract: A 17-year-old Friesian gelding was examined at a referral hospital because of a 1-month history of mild exercise intolerance and marked lymphocytosis. Physical examination revealed no peripheral lymphadenopathy or other abnormalities. Results of an abdominal palpation examination per rectum and thoracic and abdominal ultrasonographic examinations were unremarkable. B-cell chronic lymphocytic leukemia (CLL) was diagnosed on the basis of severe lymphocytosis and positive expression of the B-cell marker CD20 by lymphocytes in the bone marrow and peripheral blood. Treatment with prednisolone (2 mg/kg [0.9 mg/lb], PO, every other day) and chlorambucil (20 mg/m2, PO, every 3 weeks for 2 doses, then every 2 weeks) was initially associated with improvement in clinical signs and a decrease in the lymphocyte count. However, 3 weeks after administration of the first dose of chlorambucil, the lymphocyte count began to increase. One week later, the horse developed episodes of recurrent fever and the lymphocyte count continued to increase. Despite continued administration of the prednisolone-chlorambucil protocol, the horse's clinical condition deteriorated rapidly, and it was euthanized 6 weeks after initial examination at the referral hospital because of a poor prognosis. A necropsy was not performed. B-cell CLL has been infrequently described in horses. This report was the first to describe the use of chemotherapy, albeit unsuccessful, for the treatment of B-cell CLL in a horse. This information should be useful for guiding expectations for prognosis and management of other horses affected with the disease.
Publication Date: 2019-09-04 PubMed ID: 31478818DOI: 10.2460/javma.255.6.716Google Scholar: Lookup
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Summary
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This research article discusses the diagnosis and treatment of B-cell chronic lymphocytic leukemia (CLL) in a 17-year-old horse that exhibited mild exercise intolerance and marked lymphocytosis. Despite the use of prednisolone and chlorambucil treatment, the horse’s condition deteriorated rapidly, and it was euthanized. This report represents the first use of chemotherapy in treating B-cell CLL in a horse, providing useful information to manage similar cases.
Diagnosis
- The researchers examined a 17-year-old Friesian gelding (a type of horse) that was brought to a referral hospital. The horse had a one-month history of mild exercise intolerance and marked lymphocytosis (unusually high lymphocyte count in the blood).
- The horse was physically examined, including abdominal palpation per rectum and thoracic and abdominal ultrasonographic examinations. The results of these tests didn’t reveal any abnormalities.
- The definite diagnosis of B-cell chronic lymphocytic leukemia (CLL) was made based on severe lymphocytosis and positive expression of the B-cell marker CD20 by lymphocytes in the bone marrow and peripheral blood. This type of CLL is characterized by an excessive number of mature lymphocytes (white blood cells) circulating in the blood and infiltrating the bone marrow.
Treatment and Progression
- The horse was treated with prednisolone and chlorambucil, which are drugs used to manage lymphoproliferative disorders like CLL. Initially, this treatment led to an improvement in clinical signs and a decrease in the lymphocyte count.
- However, only three weeks after initiating the treatment, the lymphocyte count began to increase. The horse also started to show episodes of recurrent fever.
- Despite continuing the prednisolone-chlorambucil protocol, the horse’s clinical condition deteriorated rapidly. The horse had to be euthanized six weeks after the initial examination due to a poor prognosis.
Significance of the Study
- Notably, there have been few reports of B-cell CLL in horses. Consequently, this report provides valuable insights into the diagnosis and management of this disease in equine patients.
- Despite the unsuccessful outcome in this case, the research represents the first to document the use of chemotherapy for the treatment of B-cell CLL in a horse. This information can guide future prognostic expectations and treatment strategies for equine cases of B-cell CLL.
Cite This Article
APA
Long AE, Javsicas LH, Stokol T, Felippe MJB, Frimberger AE.
(2019).
Rapid clinical progression of B-cell chronic lymphocytic leukemia in a horse.
J Am Vet Med Assoc, 255(6), 716-721.
https://doi.org/10.2460/javma.255.6.716 Publication
Researcher Affiliations
MeSH Terms
- Animals
- Bone Marrow
- Chlorambucil
- Horse Diseases / diagnosis
- Horses
- Leukemia, Lymphocytic, Chronic, B-Cell / diagnosis
- Leukemia, Lymphocytic, Chronic, B-Cell / veterinary
- Lymphocytosis / diagnosis
- Lymphocytosis / veterinary
- Male
- Physical Conditioning, Animal
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