A 66-year-old man reports fatigue, blurring of vision, and epistaxis. Examination shows fundus venous engorgement with sausage-like segmentation of retinal veins. Investigations reveal Hb 8.4 g/dL, ESR 4 mm/hour, IgM level 42 g/L, and bone marrow infiltration by lymphoplasmacytic cells. The visual symptoms are explained primarily by:
- A Direct deposition of monoclonal light chains in the vitreous
- B Occlusion of central retinal artery by cryoglobulin aggregates
- C Markedly increased plasma viscosity from pentamer formation of the paraprotein ✓
- D Optic nerve compression by orbital plasmacytoma
Correct answer: C. Markedly increased plasma viscosity from pentamer formation of the paraprotein
Explanation
Waldenstrom macroglobulinemia features a monoclonal IgM paraprotein secreted by lymphoplasmacytic lymphoma cells in the marrow. Because IgM circulates as a large pentamer confined to the intravascular space, it disproportionately raises plasma viscosity, producing hyperviscosity syndrome with retinal vein sausage-linking, mucosal bleeding, and neurologic symptoms. Light chain deposition and cryoglobulins are complications of other plasma cell disorders, and orbital plasmacytoma is not part of this entity.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.