Multiple myeloma presenting as blepharitis in a horse

Abstract

A 15-year-old Thoroughbred mare presented to a referral equine veterinary hospital for reoccurring episodes of bilateral blepharitis. The patient was originally examined for a swollen left eye 3 months prior, and the referring veterinarian found no abnormalities. The swelling would resolve only to return after finishing repeated courses of topical antibiotics and dexamethasone with oral flunixin meglumine.On initial presentation, the patient was bright and alert, slightly febrile (101.6°F), tachycardic (heart rate of 50 bpm), and tachypneic (respiratory rate of 20 bpm). The horse was in excellent body condition and appeared well-hydrated. An ophthalmic examination revealed mild bilateral blepharitis, with the upper palpebrae more affected. A grade 5/6 holosystolic heart murmur was identified with normal lung auscultation. No ataxia or lameness was noted.Although not found on the initial presentation, occasional mild distal hindlimb edema was later identified on recheck examinations.Serial complete blood count (CBC, ProCyte Dx; IDEXX, Westbrook, ME, USA), biochemistry profiles (Catalyst One; IDEXX), and electrolyte profiles (iSTAT; Zoetis, Parsippany, NJ, USA) were performed during the patient's stay in the hospital. Results are presented in Table 1. The original CBC demonstrated a mild normocytic normochromic anemia (24%, reference interval 30%-47%), mild lymphopenia (1.14 K/μL; reference interval 1.50-5.10 K/μL), and mild monocytopenia (0.13 K/μL; reference interval 0.20-0.60 K/ μL). Three days later, the patient developed a mild leukopenia (4.71 K/μL; reference interval 4.90-11.10 K/μL). A blood smear evaluation on the second CBC identified marked rouleaux. The serum