27th February 2025

Paget’s disease of bone

Paget’s disease of bone is characterised by disordered localised bone remodelling leading to osteosclerotic bone. The aetiology is unclear, though some predisposing genetic factors are known. Pagetic lesions are commonly seen in the skull, spine, pelvis, femurs and tibia, though any area can be affected.

Although most are asymptomatic, some may experience pain at disease foci (often sites of muscle insertion or previous fracture). Secondary osteoarthritis due to disrupted load distribution, hearing loss, bone deformity (e.g. frontal bossing, kyphosis, bowing of the legs), and pathological fractures are all common presentations in symptomatic patients. Rarer presentations include bone overgrowth leading to nerve impingement and increased bone vascularity leading to high-output heart failure. Of note, hearing loss is less commonly sensorineural secondary to CN VIII impingement, but rather, most cases are conductive due to temporal bone osteosclerosis. Osteosarcoma is one complication that should be suspected in any patient reporting an increase in pain or new swelling, though it occurs in fewer than 1% of patients.

As most patients are asymptomatic, diagnosis is most often incidental via an isolated raised ALP or an X-ray or CT requested for another purpose. Such imaging directly visualises pagetic lesions, characterised by a mix of osteosclerosis and radiolucency ± pathological fractures. ALP may be normal if disease is minimal, restricted to a single site, or inactive (particularly post-treatment). In these circumstances, or in concurrent hepatobiliary disease, bone-specific ALP may be useful. As with osteomalacia, bone biopsy is rarely required.

Unless due to a complication of the disease (e.g. osteoarthritis or pathological fracture), pain due to a pagetic lesion, nerve impingement and hearing loss following temporal bone involvement can be treated with limited courses of bisphosphonates. Bisphosphonates may also be used before orthopaedic surgery as lesions are highly vascular and may lead to excessive blood loss. Caution is required, however, as concurrent vitamin D deficiency is common in the elderly (i.e. those susceptible to Paget’s disease), in which case bisphosphonates may result in symptomatic hypocalcaemia. Where bisphosphonates are contraindicated, calcitonin may be considered.