Dermoids are overgrowths of non-cancerous, normal skin in the wrong location that arise because of abnormal development of the embryo in utero. The skin may be pigmented, contain sebaceous and sweat glands, fat, and/or grow hair. These growths have been described in multiple species, and while affected animals are born with the condition, it may go unnoticed until the hair grows sufficiently long to become prominent or cause irritation. Any dog breed can be affected, but they occur more frequently in Australian Shepherds, German Shepherds, Cocker Spaniels, Collies, Dachshunds, Dalmatians, English Springer Spaniels, Golden Retrievers, Poodles, Pugs, Pulis, Siberian Huskies, and St. Bernards. Cat breeds more commonly affected include the domestic shorthair and Burmese.
Around the eye, they can occur as abnormal skin growing on the normal skin of the eyelids or face, on the conjunctiva, or on the cornea. They can affect the normal ability to blink, which is required for a healthy cornea, and they can be vision obstructing. In addition to affecting cosmetic appearance, the haired dermoids can be irritating. Clinical signs may include redness, tearing, discharge, and corneal ulceration. Diagnosis can be made with an ophthalmic exam.
Dermoids are typically treated in order to improve cosmesis or when the associated hair causes irritation and clinical signs. Surgical removal is the treatment of choice and is curative. Outcomes are generally good following surgical excision. Perioperative medications may include anti-inflammatories and antibiotics, depending on the location and size of the dermoid.