Advanced Paget disease of bone

A 77-year-old woman presented with longstanding left leg weakness and falls. A computed tomography scan displayed a marked widening of the diploic space of the calvaria with lytic and sclerotic regions (Figure, A and B), which is pathognomonic of advanced Paget disease affecting the skull.1,2 Her leg weakness leading to the falls was due to the expansion of the C2 vertebra, causing stenosis of the cervical spinal canal (Figure, C, arrow). The serum alkaline phosphatase level was 655 U/L (reference range, 20–175 U/L). She received zoledronic acid, resulting in normalisation of serum alkaline phosphatase levels after 12 months; however, her leg weakness did not improve.