Thymoma in a geriatric rabbit with hypercalcemia and periodic exophthalmos.

An 8-year-old rabbit was referred to an ophthalmologist because of intermittent bilateral exophthalmos and prolapse of the nictitating membranes. Both eyes could be retropulsed normally, and the exophthalmos was induced with ventroflexion. The rabbit had moderate hypercalcemia and a large mediastinal mass that could be seen on thoracic radiographs. The rabbit's condition was unchanged for 5 months. It was reexamined because of weight loss and paroxysmal coughing and, at that time, was thin and tachypneic, and had reduced thoracic compliance. Thoracotomy was performed, and a 5-cm-diameter encapsulated mass, subsequently determined histologically to be thymoma, was removed. The rabbit was euthanatized after surgery because of complications. The periodic exophthalmos and hypercalcemia in this rabbit were believed to be paraneoplastic syndromes.