Leontiasis Ossea, also known as leontiasis or lion face, is a rare meical condition, characterized by an overgrowth of the facial and cranial bones. It is not a disease in itself, but a symptom of other diseases, including Paget's disease, fibrous dysplasia, hyperparathyroidism and renal osteodystrophy, and is also seen in patients who have advanced lepromatous leprosy.