Ectopic tooth in nondentate areas is uncommon. Odontogenic keratocyst arising from impacted tooth in the inferior border of orbit is very rare. This article reports the case of a 22-year-old female with odontogenic keratocyst arising from an impacted left maxillary third molar in the inferior border of the orbit causing symptoms of chronic sinusitis. The patient also had myasthenia gravis which confounded the diagnosis. The cyst was surgically enucleated along with the tooth which relieved the symptoms of the patient.