An Uncommon Osseous Frontal Sinus Tumor: Monostotic Paget’s Disease

Paget's disease of the bone is a disorder characterized by abnormal breakdown and formation of bone tissue. The cause is believed to be either viral or genetic in origin. Most of the time, patients are asymptomatic. Diagnosis is supported by findings from multiple modalities including serum markers, imaging, bone scans, and histology. We present a rare case of Paget's disease of the bone involving the frontal sinus. We review the relevant clinical, diagnostic, and histological findings. We also suggest indications for the management of monostotic Paget’s disease of the frontal sinus. 1. Introduction Paget’s disease of the bone (PDB), first described in 1877 by the English surgeon Sir James Paget, has been defined as a disorder of bone remodeling. Characteristically, PDB begins with accelerated bone resorption followed by compensatory bone formation leaving behind a structurally disorganized bone matrix. The disease is most prevalent in western Europe, where it affects more men than women (1.8？:？1) and it is most commonly diagnosed after the fifth decade of life [1]. The diagnosis of PDB can be made based on multiple modalities including elevated serum alkaline phosphatase, urinary markers, radiologic findings, radionuclide bone scans, and pathology. PDB involves a single bone (monostotic) in 10–35% of cases, but a multifocal (polyostotic) presentation affecting 2 or more bones is more common. Although the disease can affect any bone in the body, PDB has a predilection for the axial skeleton with skull involvement being the fifth in order of frequency [1]. We report an extremely rare case of PDB of the frontal sinus. 2. Case Report A 39-year-old female was seen in consultation after having presented to the emergency department with complaints of left-sided headache and left facial paresthesias. A head computed tomography (CT) scan revealed an osseous mass in the left frontal and anterior ethmoid sinus extending into the right frontal sinus (Figures 1 and 2). An MRI of the brain identified a left-sided frontal sinus tumor that was benign in appearance and of bone origin (Figure 3). Radiologic impression was a fibro-osseous lesion either representing a fibrous dysplasia or an atypical osteoma. On examination, the patient had no facial asymmetry with no facial nerve dysfunction and she reported some paresthesias on the left side on sensory exam in the V1 distribution. Flexible nasal endoscopy was normal on the right and showed a slightly irregular edematous mucosa in the left superoanterior surface of the bulla ethmoidalis. A specific mass was not