- Pathophysiology
- Low-grade B-cell lymphoma (lymphoplasmacytic) causing massive production of monoclonal IgM paraprotein.
- Associated with MYD88 gene mutation.
- Large size of IgM pentamers leads to hyperviscosity syndrome.
- Clinical Features
- Older adults. Often asymptomatic.
- Hyperviscosity Syndrome: Blurry vision, headaches, dizziness, mucosal bleeding (nasal/gingival).
- Constitutional “B” symptoms (fever, night sweats, weight loss).
- Anemia (from marrow infiltration), peripheral neuropathy, hepatosplenomegaly.
- Diagnostics
- Serum Protein Electrophoresis (SPEP): IgM M-spike.
- Bone marrow biopsy: >10% clonal lymphoplasmacytic cells.
- Key Distinction from Multiple Myeloma
- WM: IgM spike, hyperviscosity, NO lytic bone lesions, NO hypercalcemia.
- MM: IgG or IgA spike, lytic bone lesions, hypercalcemia, renal failure.
- Treatment
- Asymptomatic: Observe.
- Symptomatic/Hyperviscosity: Plasmapheresis (acute), followed by chemoimmunotherapy (e.g., Rituximab, BTK inhibitors like Ibrutinib).