Monostotic Paget Disease of the Lumbar Vertebrae: A Pathological Mimicker

Paget disease is a metabolic disorder involving abnormal bone turnover that consists of 3 phases: the initial lytic phase, the intermediate mixed phase, and the chronic sclerotic phase. Paget disease mostly presents as polyostotic or monostotic lesions of the spine, and is rare on the Indian subcontinent. We present a case of isolated Paget disease of the lumbar third vertebra, which was confirmed only at biopsy. The patient presented with chronic low backache with a developing neurological deficit. We managed the patient with posterior spinal stabilisation, using pedicular screws and vertebroplasty of the collapsed vertebrae to regain the height. Upon the diagnosis of Paget disease, the patient was treated with calcitonin and bisphosphonates for 3 months, along with regular monitoring of alkaline phosphatase levels. Through this case, we hope to emphasize that Paget disease should be considered in the differential diagnosis of lytic lesions. Additionally, the alkaline phosphatase level in this patient was high-normal, which was an aspect of the role of Paget disease as a mimicker. Confirmatory biopsy is mandatory in all lesions.