A 6.5-year-old 10-kg (22-lb) castrated male mixed-breed dog was referred for evaluation of persistent lethargy, vomiting, thrombocytopenia, anemia, and pyrexia of approximately 1 month's duration. Treatments administered prior to referral included oral administration of the antiemetic metoclopramide hydrochloride (0.5 mg/kg [0.23 mg/lb], q 12 h) and amoxicillin (25 mg/kg [11.4 mg/lb], q 12 h) for 1 week, followed by oral administration of prednisone (2 mg/kg [0.9 mg/lb], q 12 h) for 1 week. Intermittent seizures began during treatment with prednisone; the frequency of drug administration was decreased (2 mg/kg, q 24 h) 3 days prior to referral.