The brown tumor, also known as osteoclastoma, is a local and benign lesion of the bone. It appears as a consequence of an increase in osteoclastic activity and fibroblastic proliferation in the context of severe primary or secondary hyperparathyroidism (2ndHPTH), the latter occurring in chronic kidney disease (CKD) due to decreased vitamin activity D at the renal level, with decreased phosphorus excretion and a tendency to hypocalcemia, which stimulates the growth of parathyroid glands. By microscopy the brown tumor is characterized by an increase in osteoclast activity, expansion of bone resorption and formation of new bone tissue; there are irregularities in the of the trabecular tissue thickness and peritrabecular fibrosis. The presence of multinucleated giant cells and interstitial hemorrhage with hemosiderin deposits gives it the characteristic brown appearance.1,2

Complete regression or disappearance of the brown tumor usually occurs after parathyroidectomy, although depending on the location and local destruction capacity, it can cause compression or pathological fractures. Generally, it is a multiple lesion that preferentially affects the ribs, clavicles, mandible and pelvis3; orbital involvement is infrequent.2

We present the case of a 27-year-old woman with CKD secondary to nephronoptisis that underwent 2 renal transplants, the first one anticipated at 7 years of age and the second at 9 years, with loss of both due to chronic graft nephropathy. She finally started hemodialysis at 23 years of age. After 4 years on hemodialysis and with a history of more than 5 months of evolution, the patient showed severe secondary HP with a maximum PTHi of 4876pg/ml, hypercalcemia and normo- and hyperphosphatemia that is not controlled despite treatment with cinacalcet, vitamin D analogs and phosphate binders. 99mTc-sestamibi scan shows pathological uptake of the radiotracer in all parathyroid glands demonstrating a polyglandular hyperplasia. In addition, physical examination is remarkable for the progressive and pronounced appearance of an exophthalmos with caudal displacement of the left orbit and a decrease in vision. Reconstructive orthopedic CT (Fig. 1) and MRI describe several cystic-looking bone radiolucent lesions of 3 left periorbital brown tumors located respectively in the orbit ceiling with extension to the ipsilateral frontal sinus, In the left upper jaw and in the ascending branch of the left mandible with secondary arterial occlusion. With these findings, a total parathyroidectomy was performed with suprasternal autotransplantation to control 2nd HPTH and to achieve the reduction of tumors. After the intervention, PTHi levels fall rapidly with development of a hungry bone syndrome that requires high doses of calcium, vitamin D and hemodialysis with calcium of 1.75μmol/l, which ensures the success of the intervention. Two months later, the analytical improvement is not accompanied by reduction of clinical symptoms; exophthalmos and compressive optic neuropathy continues. The CT scan shows an increase in size of the orbital ceiling lesion requiring excision. Microscopic examination revealed brown bone tumor.

Fig. 1.

Cranial and orbital CT with pre-surgery reconstruction.

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At present, only 19 cases have been described with periorbital involvement. In most cases, tumor excision is performed, although other different locations are described in which with the total parathyroidectomy has been followed by remission of the bone lesion.3–5

Our case was resolved with parathyroidectomy and tumor excision (Fig. 2). The prevalence of brown tumor in patients with 2ndHPTH is 1.5–13% in CKD,1 being more frequent in young women.6 However, a cautious differential diagnosis should be made and rule out bone tumor implants. Nowadays, the measurement of and the effective treatment of 2ndHPTH, the appearance of new cases is decreasing.7

Fig. 2.

Cranial and orbital CT with post-surgery reconstruction.

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