Ocular and multicentric lymphoma in a young racehorse.

The research article presents a case of ocular and multicentric lymphoma in a 6-year-old thoroughbred racehorse, explaining its recognition, diagnosis, treatment, and progression to severe illness, leading to euthanasia. The study emphasizes the importance of considering intraocular and systemic lymphoma in the differential diagnosis of horses with anterior uveitis, especially when traditional treatment fails and other systemic signs of illness emerge.

Initial Symptoms and Diagnosis

• The 6-year-old thoroughbred gelding initially showed signs of blepharospasm (involuntary blinking or spasm of the eyelids) and opacity in the left eye, which indicated acute uveitis, an inflammation of the middle layer of the eye.
• An ophthalmic examination confirmed this diagnosis, after which conventional treatment was begun. This regimen included systemic antibiotics, anti-inflammatory drugs, topical mydriatics (drugs that dilate the pupil), and corticosteroids.

Progression of the Disease

• Over the 4-week treatment period, the horse’s response to the treatment was weak. Further complications arose, such as cellulitis (skin infection) in the right hind limb, fever, weight loss, and dependent edema (swelling due to fluid accumulation).
• Blood tests indicated a presence of liver disease.
• An ultrasound of the abdomen revealed severe splenomegaly (enlarged spleen) and slight hepatomegaly (enlarged liver).
• The diagnosis of malignant T-cell lymphoma was confirmed with a liver biopsy.

Euthanasia and Postmortem Examination

• Given the deterioration in the horse’s general condition, euthanasia was performed. A postmortem examination followed.
• The necropsy and histologic (microscopic) examination revealed that the horse had multicentric lymphoma, a cancer that originates in the lymphatic cells and affects multiple sites in the body. In this case, the spleen, mesenteric lymph nodes, and both eyes were involved.

Implications of the Study

• These findings stress the need to consider intraocular and systemic lymphoma in the differential diagnosis when a horse presents with anterior uveitis. This is especially applicable when the uveitis does not respond to conventional treatment and other signs of systemic illness appear.
• The study suggests that cytological examination of the aqueous humor (liquid in the front part of the eye) may rapidly diagnose intraocular lymphoma in eyes showing clinical uveitis.