What causes Leontiasis ossea in the craniofacial bones on CT?
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Answer:
Leontiasis ossea represents diffuse overgrowth and bony expansion of the facial bones, particularly the maxilla, resulting in a lion-like facial appearance; it is most commonly caused by fibrous dysplasia but also occurs in Paget disease, secondary hyperparathyroidism from renal osteodystrophy (uremic leontiasis ossea), and rarely acromegaly.
Why is it called so?
The term derives from Greek “leon” meaning lion and “iasis” meaning condition, due to the progressive facial bony overgrowth producing a coarse, thickened, lion-like facial appearance with maxillary hypertrophy, saddle nose deformity, and encroachment on orbits, nasal cavities, and sinuses.
Pathophysiology
Uncontrolled osteoclastic bone resorption alternates with excessive osteoblastic bone formation and sclerosis, driven by underlying conditions like fibrous dysplasia (fibro-osseous proliferation), Paget disease (disordered remodeling), or secondary hyperparathyroidism (elevated PTH causing high-turnover bone disease with osteitis fibrosa cystica); this produces marbled bony expansion with alternating hyper- and hypoattenuating zones, serpiginous tunneling, and loss of corticomedullary differentiation on CT.
Alternative names: Lion face syndrome
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