Follicular choristoma in the third eyelid of an eclectus parrot ().

Case Description: A 1-year-old male eclectus parrot () with a 3- to 4-month history of blepharospasm in the right eye was referred to a veterinary medical teaching hospital for further evaluation. Conventional medical treatments had been ineffective. The referring avian specialist had plucked a suspected ectopic feather from the right eye 6 weeks prior to the referral evaluation.

Clinical Findings: The parrot was sedated, and ophthalmic examination of the right eye with slit-lamp biomicroscopy revealed a 3 × 2 × 2-mm raised vascular mass with a focally pigmented center associated with the temporal aspect of the leading edge of the third eyelid. No abnormalities were detected in the left eye.

Treatment And Outcome: The parrot was anesthetized, and the right eye mass was excised and submitted for histologic examination. Histologically, there was a single pigmented feather follicle bulb surrounded by multiple discrete lymphoid follicles and moderate lymphoplasmacytic inflammation within the substantia propria of the third eyelid conjunctiva. The histologically normal feather follicle in an abnormal location classified the lesion as a choristoma. Nine months after surgery, the parrot had no signs of ocular discomfort and no overt regrowth of the feather follicle.

Clinical Relevance: For the eclectus parrot of this report, a lesion caused by normal differentiation of an ectopic feather follicle in the right third eyelid was successfully treated. A third eyelid choristoma appears to be a hitherto unreported pathological finding in avian species. Although rare, the presence of a choristoma should be considered as a differential diagnosis for birds with blepharospasm.