Osteolytic lesions in multiple myeloma result primarily from which mechanism?

• A Direct resorption of bone by malignant plasma cells
• B Myeloma cell induced upregulation of RANKL and suppression of osteoprotegerin in the bone marrow microenvironment ✓
• C Secondary hyperparathyroidism driven by renal failure from cast nephropathy
• D Deposition of amyloid light chain in trabecular bone triggering osteoclastic resorption

Explanation

Myeloma cells and marrow stromal cells increase RANKL expression while reducing osteoprotegerin, the soluble decoy receptor for RANKL. This tips the RANKL to OPG balance toward osteoclast activation, producing purely lytic lesions that are typically cold on bone scan because there is little osteoblastic repair. Plasma cells do not themselves resorb bone, and parathyroid hormone is not the driver of these focal lesions.

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.