Dysthyroid orbital disease in Macaca fascicularis.

Fluctuating left exophthalmos in a mature male Macaca fascicularis was studied clinically utilizing the diagnostic modalities of A- and B-scan ultrasonography and computerized tomography in addition to routine ophthalmic examination and radiography. Laboratory results were suggestive of thyroid hypofunction. Clinical and histopathologic observations were consistent with a diagnosis of dysthyroid orbitopathy, a condition previously unreported in nonhuman primates and the most common cause of unilateral exophthalmos in humans.