A 60-year-old man is found to have an IgM paraprotein of 2 g/dL with 15% lymphoplasmacytic cells in bone marrow but no lytic lesions, anaemia, or hyperviscosity symptoms. Serum viscosity is normal. This condition is best classified as:

• A Multiple myeloma, IgM type
• B Smouldering Waldenström macroglobulinaemia ✓
• C Monoclonal gammopathy of undetermined significance (MGUS)
• D Waldenström macroglobulinaemia

Explanation

Smouldering (asymptomatic) Waldenström macroglobulinaemia is diagnosed when bone marrow lymphoplasmacytic infiltration is ≥10% and/or serum IgM is ≥3 g/dL but no end-organ damage (anaemia, hyperviscosity, neuropathy, cryoglobulinaemia) is present; this case with 15% BM involvement but <3 g/dL IgM and no symptoms fits the smouldering category. Symptomatic WM requires evidence of disease-related organ dysfunction. MGUS is defined as <10% BM involvement and IgM <3 g/dL.

Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.