Imaging Case Study of the Month Isolated Unilateral Fibrous Dysplasia of the Sphenoid Sinus

INTRODUCTION Fibrous dysplasia as a clinical term was introduced by Lichtenstein as early as 1938. The disease is characterized by a slowly progressive replacement of cancellous bone by abnormal fibrous tissue that histologically represents various stages of bone metaplasia. The proportions of the fibrous and osseous tissues vary, occasionally even in the same bone.· The development of the disease lasts for years and presents with deformity or mild symptoms. This locally destructive disease can occur in association with endocrine abnormalities such as Albright's syndrome (precocious puberty, cutaneous pigmented patches over the involved bones) or as an isolated clinical entity. Rarely, fibrous dysplasia is associated with other bone pathological changes such as aneurysmal bone cyst inside the paranasal sinuses or mucocele. The cause of the disease, however, remains unknown.