A patient presents with bone pain, kidney dysfunction, monoclonal gammopathy, and lytic bone lesions. What is the most likely diagnosis?

• A. Osteoporosis
• B. Multiple myeloma
• C. Osteosarcoma
• D. Leukemia

Answer: (B)

This presentation points to a malignant plasma cell disorder that causes bone destruction and kidney injury. The combination of bone pain with lytic lesions, kidney dysfunction, and a monoclonal gammopathy is classic for multiple myeloma. Malignant plasma cells proliferate in the marrow and produce a single type of immunoglobulin (monoclonal protein), which can deposit in the kidneys as light chains and promote renal failure. In bone, these cells activate osteoclasts, leading to osteolytic lesions and persistent pain.

Osteoporosis wouldn’t explain a monoclonal protein or the specific kidney injury. Osteosarcoma is a primary bone tumor more common in younger patients and has distinct radiographic features, not a monoclonal spike. Leukemia can cause bone pain and systemic symptoms but typically lacks a monoclonal gammopathy with lytic bone lesions.