Most Common Bone Lesion in Multiple Myeloma
Osteolytic (lytic) lesions are the most common bone lesion in multiple myeloma, present in approximately 80-90% of patients at diagnosis. 1, 2
Characteristics of Lytic Lesions
Lytic lesions appear as "punched-out" osteolytic defects on imaging with the following features:
- Well-defined, round radiolucent areas without sclerotic borders, often described as having a "raindrop" or "Swiss cheese" appearance 2
- Only become visible on conventional X-ray after more than 50% of trabecular bone has been lost 2
- Result from increased osteoclastic activity with suppressed osteoblastic function 2
Pathophysiology
The unique aspect of myeloma bone disease distinguishes it from other malignancies:
- Increased osteoclastic bone resorption occurs simultaneously with decreased or absent osteoblast activity 3
- Once tumor burden exceeds 50% in a local area, osteoblast activity is either suppressed or absent 3
- This creates lytic bone destruction that is not followed by reactive bone formation, resulting in extensive lytic lesions 4
Clinical Presentation
Lytic lesions manifest in approximately 90% of MM patients and lead to significant complications 1, 5:
- Severe bone pain
- Pathologic fractures
- Vertebral collapse
- Hypercalcemia
- Spinal cord compression
Imaging Detection
Whole-body low-dose CT (WBLD-CT) is now the standard for detecting lytic lesions (grade 1A recommendation), as it:
- Detects up to 60% more relevant findings than conventional radiography 2
- Provides high-resolution images of cortical and trabecular bone 1
- Can identify small (<5 mm) lytic bone lesions 1
Important Caveat
Plain radiography has significant limitations as it only reveals lytic disease when over half of the trabecular bone has been lost 1. This results in underdetection of early bone disease and generalized osteopenia 1.
Management Implications
All myeloma patients with adequate renal function and bone disease at diagnosis should be treated with zoledronic acid or pamidronate (grade 1A recommendation) 1. These bisphosphonates work by inhibiting osteoclastic bone resorption, though they do not stimulate new bone formation 6.