29th May 2023

Pre-malignant disorders of plasma cells

Monoclonal gammopathy of undetermined significance (MGUS)

All multiple myeloma is now believed to progress through an asymptomatic premalignant stage called MGUS. Patients with MGUS have a clonal population of plasma cells producing a paraprotein (<30 g/L). There is a 1% risk of progression to myeloma per year. By definition, there must not be evidence of end organ damage.

Smouldering myeloma

An intermediate stage with a paraprotein >30 g/L or plasma cells >10% and <60% in bone marrow but without evidence of end organ damage. The risk of progression to overt myeloma is around 10% per year in the first 5 years but actually decreases after this point.