QUIZ: No. 12, 18/05/2025

Paget’s Disease of the Proximal Humerus (Mixed Phase)

Findings: Coarsened trabecular pattern with thickened bony trabeculae, cortical thickening and expansion of the proximal humerus with preserved overall bone shape. Patchy areas of increased density (sclerosis) and lucency (lysis) indicating the mixed phase. Absence of fracture, periosteal reaction or significant soft tissue mass. MRI demonstrates bone marrow changes, cortical thickening, and heterogeneous signal intensity consistent with Paget’s disease. No signs of soft tissue extension, pathological fracture, or malignant transformation.

Paget’s disease of bone is a chronic skeletal disorder characterized by abnormal bone remodeling, leading to structurally disorganized and weakened bone.

Radiologic findings include cortical thickening, bone expansion, coarsened trabeculae, and a mixed lytic-sclerotic pattern, especially in weight-bearing bones like the pelvis, spine, and proximal long bones. MRI reveals marrow signal alterations and heterogeneous intensity without soft tissue extension, while CT provides detailed visualization of cortical thickening and trabecular distortion. Biochemically, patients often show elevated serum alkaline phosphatase with normal calcium and phosphate levels.

Differential diagnoses include fibrous dysplasia (typically younger patients with ground-glass matrix), metastatic lesions (multiple, aggressive, often with soft tissue mass), and osteomyelitis (infective features with systemic signs).

Early diagnosis and differentiation are essential to prevent complications like deformity, fracture, and rare malignant transformation.