osteolytic

Osteolytic describes a process or lesion in which bone is destroyed or resorbed, producing radiolucent areas on imaging. It is often used to characterize radiographic findings of osteolysis or lytic bone lesions, in contrast to osteoblastic (sclerotic) lesions which indicate new bone formation.

Osteolysis results from increased activity of osteoclasts or decreased bone formation, frequently driven by inflammatory cytokines and signaling pathways such as RANK/RANKL/OPG. It may be focal or multifocal and can involve any skeletal site.

Common causes include malignant processes (bone metastases from breast, lung, kidney, thyroid cancers; multiple myeloma and plasmacytoma), infectious osteomyelitis, benign bone lesions (unicameral bone cyst, giant cell tumor), and metabolic or endocrine disorders (hyperparathyroidism). Pediatric eosinophilic granuloma and Langerhans cell histiocytosis can present with focal osteolysis. Traumatic injury and radiation can also create osteolytic changes.

Imaging evaluation starts with plain radiographs to identify lucent areas; CT helps delineate cortical destruction and matrix; MRI assesses marrow involvement and soft tissue extension; bone scintigraphy or FDG-PET can detect additional lesions. Definitive diagnosis often requires biopsy with histopathology and laboratory tests directed at suspected causes.

Management targets the underlying cause and may include surgery to stabilize bone or debulk a lesion, radiation therapy for certain metastases, systemic therapies for cancer, antibiotics for osteomyelitis, and agents that reduce osteoclast-mediated resorption such as bisphosphonates or denosumab. The prognosis depends on etiology and extent of bone involvement.