Fibrous dysplasia of the frontal bone.

Abstract

Fibrous dysplasia typically occurs in patients between the ages of 5 and 15 years. We report the case of a middle-aged woman with longstanding monostotic fibrous dysplasia who responded well to conservative treatment. She had presented with a very long (15 yr) history of frontal headache and pressure over the frontal sinus. On examination, a protuberance was noted in the region of the right frontal sinus. No other symptoms were evident, and findings on the ENT examination were normal. Computed tomography (CT) detected a widening of the frontal bone with osteolytic changes of the cancellous bone of the diploe. Partial multiphase skeletal scintigraphy and single-photon emission CT of the cranium showed increased bone metabolism in the area of the right frontal bone. No other hot spots were seen. In view of the absence of any complications, no tissue biopsy was performed. The patient was prescribed bisphosphonates for symptom relief Follow-up CT 1 year later revealed no progression of the lesion. Overtreatment of fibrous dysplasia should be avoided because most patients respond to conservative management. In those cases that are refractory to medical treatment, surgery--in experienced hands--can result in a good functional and cosmetic outcome.

Introduction

Fibrous dysplasia is a rare, nonneoplastic bone disease in which osteoblasts are incapable of producing mature trabecular bone. It usually arises in patients between the ages of 5 and 15 years. Fibrous dysplasia is believed to be caused by a mutation of the gene that codes for the subunit of the Gs protein, a signal protein located on the cell membrane. The mutation leads to a loss of guanosine triphosphatase activity and thus to adenyl cyclase overactivity and subsequent overproduction of cyclic adenosine monophosphate (cAMP). It is the continuous cAMP stimulation that appears to be responsible for the onset of fibrous dysplasia. The cAMP stimulation leads to swelling of the flat bones and widening and deformation of the long bones; cortical bone remains unchanged.

In this article, we describe a case of monostotic fibrous dysplasia in a middle-aged woman who responded well to medical treatment.

Case report

A 54-year-old woman presented to our outpatient clinic with a 15-year history of frontal headache and a permanent feeling of pressure over the right frontal sinus. She had been referred to us after bony changes in the area of the right frontal sinus were found incidentally on dental x-rays. She had no history of ocular symptoms. She was taking a nonsteroidal anti-inflammatory drug for relief of chronic back pain.

Examination revealed a slight protuberance over the area of the right frontal sinus. No tenderness was evident on palpation of the supraorbital foramen. The ENT examination detected no pathology.

Computed tomography (CT) of the paranasal sinuses revealed widening of the frontal bone with extensive medial and right lateral osteolytic structural changes in the cancellous bone of the diploe (figure 1). No perforation of the internal or external lamina was noted, although the external lamina was markedly eroded.

[FIGURE 1 OMITTED]

Partial multiphase skeletal scintigraphy and single-photon emission CT of the cranium showed increased bone metabolism in the area of the right frontal bone, starting in the ethmoid cells in the roof of the orbit and extending slightly to the left (figure 2). Skeletal scintigraphy provided no further indication of the characteristics of the lesion. Right-sided frontal hyperostosis could not be ruled out in the differential diagnosis.

[FIGURE 2 OMITTED]

As expected, the areas of increased lysis in the frontal bone seen on coronal CT exhibited evidence of normal to decreased bone metabolism. Secondary findings included a dental focus in the right maxilla and pronounced degenerative changes in the entire vertebral column; the degeneration was most pronounced in the costovertebral joints and in the facet joints of the lumbar spine. Arthritic changes were seen in both knee joints. No other hot spots of increased bone activity were seen.

To rule out Paget's disease, assays of inorganic phosphate and calcium were obtained; both values were within normal limits (2.6 mg/dl and 2.38 mmol/L, respectively). A urine hydroxyproline assay also yielded a normal result of 2.7 nmol (range of normal: 2.5 to 9.5).

The final diagnosis of fibrous dysplasia was established by tissue biopsy. The patient was prescribed bisphosphonates for symptom relief. At follow-up 1 year later, the patient remained asymptomatic, and CT found no evidence of lesion progression. The patient was scheduled to undergo yearly follow-up CTs indefinitely.

Discussion

Fibrous dysplasia of the bone (Jaffe-Lichtenstein syndrome, osteodystrophia fibrosa) was first described by Lichtenstein in 1938. (1) It accounts for approximately 2.5% of all bone tumors, and familial cases have been reported. (2) Fibrous dysplasia typically occurs in patients between the ages of 5 and 15 years, and it spontaneously resolves during puberty in 60 to 80% of patients. (2) Most of these tumors arise unilaterally in the skull and femoral bones. The incidence of craniofacial manifestations of fibrous dysplasia ranges between 10 and 32%. (3)

The disorder is classified clinically as either monostotic or polyostotic.

The monostotic form occurs in 70 to 80% of patients. (1,2) It generally occurs during the second decade of life and becomes dormant by the third decade. Hormonal changes, such as those seen in pregnancy, can reactivate a dormant lesion. (3)

The polyostotic form most often affects the skull and facial cranium; the pelvis, spine, and shoulder girdle have also been involved, but involvement of the extremities is rare. Patients with the polyostotic form generally present with numerous head and neck symptoms, such as a loss of hearing, recurrent sinusitis, nasal obstruction, protrusio bulbi, or compression of the optic nerve, which can lead to blindness. (4) In a few cases, the polyostotic form has been associated with endocrinopathies. A special type of polyostotic fibrous dysplasia is McCune-Albright syndrome, which is associated with precocious sexual development and cafe au lait spots on the skin. (5) The cause is believed to involve a point mutation on chromosome 20 (20q12-q13) within the Gs alpha region; as a result of the mutation, the activity of the Gs protein, and thus of adenyl cyclase, is increased.

The diagnosis in our patient was established on the basis of the history, physical examination, and radiologic, laboratory, and pathologic investigations. The diagnostic tests we performed were ordered to rule out involvement of important anatomic structures, such as the optic nerve. When we were unable to find any such complications, we prescribed symptomatic pain therapy, mainly bisphosphohates. Surgical excision of this slowly growing benign tumor was not indicated in this case. Findings at the 1-year follow-up confirmed that watch-and-wait is an acceptable policy in cases of fibrous dysplasia.

Bisphosphonates are potent inhibitors of bone absorption. (4,6) In adults, general metabolic disorders such as osteoporosis and Paget's disease are increasingly being treated with bisphosphonates (e.g., pamidronate), (7) When surgery is indicated, it should be relatively conservative in light of the benign nature of this disease and its excellent response to medical therapy. Important goals of surgery should be the preservation of existing function and avoidance of cosmetic deformity.

References

(1.) Lichtenstein L. Polyostotic fibrous dysplasia. Arch Surg 1938;36:874-98.

(2.) Enderle A, Willert HG, Zichner L. Angeborene und erworbene Skeletterkrankungen. In: Witt AN, Rettig H, Schlegel KR, et al, eds. Orthopadie. Stuttgart; New York: Georg Thieme Verlag; 1984:91-124.

(3.) Pecaro BC. Fibro-osseous lesions of the head and neck. Otolaryngol Clin North Am 1986;19:489-96.

(4.) Riminucci M, Fisher LW, Shenker A, et al. Fibrous dysplasia of bone in the McCune-Albright syndrome: Abnormalities in bone formation. Am J Pathol 1997;151:1587-1600.

(5.) Delmas PD. Bisphosphonates in the treatment of bone diseases. N Engl J Med 1996;335:1836-7.

(6.) Rauch F, Schoenau E, Glorieux FH. Bisphosphonate--Anwendung in der Paediatrie. Monatsschr Kinderheilkd 2000;148:334-41.

(7.) Chapurlat RD, Delmas PD, Liens D, Meunier PJ. Long-term effects of intravenous pamidronate in fibrous dysplasia of bone. J Bone Miner Res 1997; 12:1746-52.

John M. Hempel, MD; Petros D. Karkos, MPhil, AFRCSI; Wolfgang J. Issing, MD

From the Department of Otorhinolaryngology-Head and Neck Surgery, Ludwig-Maximilians-University, Munich (Dr. Hempel), and the Department of Otolaryngology-Head and Neck Surgery, The Freeman Hospital, Newcastle upon Tyne, U.K. (Mr. Karkos and Dr. Issing).

Reprint requests: Mr. Petros D. Karkos, Specialist Registrar in Otolaryngology, 36 Hopkinsons Court, Walls Ave., Chester CH1 4LN, UK. Phone: [phone]; e-mail: [e-mail]