Question category: Haematology
A 68 year old male is found to have raised IgG levels. An IgG paraprotein band (2.5g/L) is found on serum protein electrophoresis. He is otherwise well and asymptomatic. His Us and Es and calcium levels are normal. There is no evidence of Bence Jones protein in the urine. A recent X-ray of his lumbar spine shows no evidence of osteolytic lesions. What is the most likely diagnosis?