A 68‑year‑old man is referred to the haematology clinic by his GP with a 3‑month history of worsening fatigue and back pain. He reports that the back pain is dull and persistent, worse at night, and not relieved by rest. Over the past few weeks, he has noticed increasing thirst and passing urine more frequently. He has also unintentionally lost 5 kg in the last 2 months. On examination, he appears pale. There is localised tenderness over his thoracic spine but no neurological deficit. There is no lymphadenopathy or hepatosplenomegaly.