Fibrous dysplasia with a secondary aneurysmal bone cyst (ABC). A) The patient with a history of MAS complained of visual changes. Worsening asymmetry of the left eye and face was noted, and an on examination he was noted to have vertical dystopia of the orbit in the preoperative photograph. He was found to have a rapidly growing ABC within FD and underwent immediate resection and decompression of the ABC. B) The asymmetry and symptoms resolved after surgery. Note the classic café au lait spots of the left face and neck region as part of the triad of MAS. C&D) Preoperative CT images of the patient in A showing the FD lesion and associated ABC. Note the fluid/fluid level diagnostic of an ABC (arrows). The association of an ABC often results in aggressive behavior and rapid enlargement of the FD lesion with displacement of adjacent structures, in this case, the eye.