A 62-year-old man with multiple myeloma has severe back pain. Radiographs show punched-out lytic lesions in the skull, spine, and pelvis. A radionuclide bone scan is unexpectedly negative despite extensive disease. The best explanation for these findings is:

• A Osteoblastic activation by tumor-derived endothelin-1 exceeds resorption
• B Renal failure reduces tracer excretion and washes out skeletal signal
• C Denosumab therapy given before staging masks lesion uptake
• D Purely osteolytic lesions with suppressed osteoblastic activity produce no uptake on bone scan ✓

Explanation

Myeloma bone disease is driven by osteoclast activation through RANKL overexpression and MIP-1 alpha secretion by stromal cells and plasma cells, while Wnt antagonists such as DKK1 suppress osteoblast activity. Radionuclide bone scans detect osteoblastic turnover, so purely lytic myeloma lesions appear cold or negative. Endothelin-1 drives osteoblastic metastases seen in prostate cancer, the opposite pattern.

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.