Toxic flare phenomenon in osteoblastoma: A case report with literature review

Abstract

Osteoblastomas are benign neoplasm of the bone that is characterized by clinical and histological similarity to osteoid osteomas. They are larger (>1.5–2 cm) and tend to affect the axial skeleton. Patients typically present commonly in the second or third decades of life with a male predilection. The flare phenomenon in osteoblastoma is a rare but known entity showing florid multifocal periostitis. Few cases have been reported in the literature. Focally aggressive osteoblastomas also present with flare phenomenon mediated by prostaglandin-induced inflammation. We report a strikingly unusual case of an osteoblastoma of the spine in a 23-year-old male patient who presented in our outpatient department with complaints of low backache, weight loss, intermittent stiffness, and fever for the past year. The patient was HLA-B27 positive, diagnosed as ankylosing spondylitis, and clinical symptoms were attributed to sacroiliitis. However, his fever and weight loss, while on treatment, were unexplained. Roentgenogram, computed tomography, and magnetic resonance imaging of the patient depicted a large bone tumor centered at the junction of the right pedicle and transverse process of L5 vertebra, associated with severe reactive marrow edema, periosteal reaction, periostitis, and sclerosis in the posterior vertebral elements also extending into the L4 vertebra. The lesion was suspected to be osteoblastoma with close imaging differential as osteosarcoma. CT-guided biopsy proved osteoblastoma with acute local toxic flare.