Clinical Case  A 5-year-old patient presented with history of glabellar soft tissue fullness and nasal bone abnormality.  Right side of the forehead was slightly advanced as compared to the left in the supraorbital region.  CT done at age of 1 month, eventually diagnosed as melorheostosis.  A non-contrasted maxillofacial cone beam CT study done at the age of 5 years. Field-of-view extended from level of frontal bone to that of C3-C4. Osteosclerotic Bone Dysplasia (Melorheotosis) of the Craniofacial Bones Katkar R, Pannu V*, Nair MK Oral and Maxillofacial Radiology, University of Florida, College of Dentistry, Gainesville, Florida Introduction  Melorheostosis: non-hereditary, rare, sclerosing bone dysplasia characterized by localized, diffuse thickening of cortical bone.  A non-genetic developmental anomaly of mesodermal origin with an early childhood onset, mainly affecting diaphyses of long bones, and bones of hand and feet unilaterally. Recently, it has been established that it is due to a loss-of- function mutation in LEMD3 gene.  May be monostotic, monomelic or polyostotic and the lesions follow the innervation of spinal sensory nerves. This condition is often asymptomatic, although pain, stiffness, limitation of motion and deformity may be present.  Radiographic features involving long bones most commonly present as longitudinal hyperostotic bars resembling molten wax flowing down the side of a candle.  In the craniofacial region, it can present as either a homogenous sclerosis or as zones of irregular sclerosis. Dense foci of abnormal sclerotic bone consist of cortical and medullary hyperostosis involving facial bones in a sequential manner, accompanied by overlying soft tissue prominence of affected bones.  Most cases do not require surgical intervention. In some rare and complicated cases, corrective surgery is required. Discussion  Sclerosing bone dysplasias are a unique set of skeletal abnormalities with a wide range of radiologic, clinical, and genetic characteristics.  Melorheostosis is rare in the craniofacial region. First described by Leri and Joanny in  Literature review revealed about 400 cases of Melorheostosis with less than 10 associated with craniofacial manifestations.  Radiographic findings usually sufficient to reach definitive diagnosis in younger patients. CT reveals clear demarcation from normal bone.  Primary goal of treatment is symptomatic relief.  Prognosis of melorheostosis depends on anatomical location, extension into soft tissues, and soft tissue changes. It does not shorten life span. The disease exhibits a slow, chronic course, with periods of exacerbation and arrest. Recurrence is usually expected after operative excision. Malignant transformation is rare.  When alveolar processes of the mandible and the maxilla are involved, eruption of teeth and orthodontic movement could pose clinical challenges. References 1.J. J. Kuttenberger, N. Hardt, J.-O. Gebbers, B. Hofer: Osteosclerotic bone dysplasia (melorheostosis) of the mandible. Int. J. Oral Maxillofac. Surg. 2006; 35: 1164–7. 2.Mariaud-Schmidt RP, Bitar WE, Perez-Lamero, Barros-Nunez P. Melorheostosis: unusual presentation in a girl. Clin Imaging 2003;27: Ethunandan M, Khosla N, Tilley E, Webb A. Melorheostosis involving the craniofacial skeleton. J Craniofac Surg 2004; 15: Williams JW, Monaghan D, Barrington NA. Cranio-facial melorheostosis: case report and review of the literature. Br J Radiol 1991;64: Brown RR, Stener GC, Lehman WB. Melorheostosis: case report with radiologic- pathologic correlation. Skeletal Radiol 200;29: Radiographic Findings  Multiple high attenuation foci resembling compact bone in midline and extending to the left side of the sphenoid, frontal, and ethmoid bones, anterior maxilla and anterior mandible with bony enlargement.  Sphenoid and left maxillary sinuses show inadequate pneumatization.  Mucosal thickening is noted in the bilateral maxillary sinuses, ethmoid air cells, and sphenoid sinus.  Dripping candle wax sign, which is characteristic of melorheostosis can be appreciated as well.  Bone in the region of teeth #s and 9-10 appears sclerotic with evidence of expansion.  Multiple unerupted teeth noted. A malformed supernumerary tooth is noted in anterior maxilla, apical and palatal to developing #9.  Slight asymmetry of the calvarium is noted. Differential Diagnosis  In most cases, diagnosis is based on radiographic and clinical findings and a biopsy is not required.  Increased bone density conditions which may simulate osteosclerotic bone dysplasia as presented in this young patient, include:  Polyostotic fibrous dysplasia: mixed density lesion with ground glass or orange peel appearance.  Sclerosing osteomyelitis: reactive sclerosis with layers of subperiosteal bone.  Fluorosis: osteosclerosis of tissue surrounding affected bone, large pulp chambers, prominent marrow space, thickened cortical plate  Osteoid osteoma: small radiolucency with central calcification, located in the cortical bone, and surrounded by sclerotic bone; usually painful. Multiple high density masses noted in the sphenoid bone, frontal bone, ethmoid bone, anterior maxilla, and anterior mandible. Dense sclerotic mass in the sphenoid, ethmoid, and maxillary sinuses. An extensive dense radiopaque mass in the left anterior mandible with enlargement and thickening of the cortical bone. Sclerotic bone superior to developing mandibular teeth. Sclerotic and expansile bone in the maxillary and mandibular anterior region.