Causes of Musculoskeletal Pain in Paget's Disease of Bone.

Paget's disease of bone (PDB) is characterised by increased and disorganised bone remodelling leading to various complications, such as bone deformity, deafness, secondary osteoarthritis, and pathological fracture. Pain is the most common presenting symptom of PDB, but it is unclear to what extent this is due to increased metabolic activity of the disease, complications, or unrelated causes. We conducted a cross-sectional study of 168 people with PDB attending secondary care referral centres in the UK. We documented the presence of musculoskeletal pain and sought to determine its underlying causes. Musculoskeletal pain was reported by 122/168 (72.6%) individuals. The most common cause was osteoarthritis of joints distant from an affected PDB site in 54 (44.3%), followed by metabolically active PDB in 18 (14.7%); bone deformity in 14 (11.4%); osteoarthritis of a joint neighbouring an affected site in 11 (9.0%), neuropathic pain in 10 (8.2%), and various other causes in the remainder. Pain was more common in women (p<0.019) and in older individuals (p<0.001). Circulating concentrations of macrophage colony-stimulating factor (M-CSF) were significantly higher in those with pain (p = 0.008), but there was no difference between groups of patients with and without pain in concentrations of interleukin-6 (IL-6) or biochemical markers of bone turnover. Pain is a common symptom in PDB but is most often due to osteoarthritis at an unaffected site. The study illustrates the importance of fully evaluating people with PDB to determine the underlying cause of pain so that management can be tailored appropriately.