Findings: Following the intravenous administration of 24.7 mCi of technetium 99m MDP, delayed images in the anterior and posterior projections were obtained of the whole body. A single anterior view is submitted. The left femur demonstrates diffuse increase in radiopharmaceutical activity with bowing and expansion. In addition, there is increased activity within the right proximal tibia.

Diagnosis: Paget's disease.

Discussion: There are three phases in Paget's disease. These are the lytic, sclerotic and mixed phases. Typically, all three phases are hot on bone scan. However, inactive disease uncommonly demonstrates decreased activity.

Typical radiographic findings include thickening of the cortex with expansion of bone as well as bowing of the tibia and femur. Early radiographic signs are thickening of the iliopubic and ilioischial lines.

Osteoporosis circumscripta is commonly seen within the frontal bone and is characterized by increased radiopharmaceutical activity.

In general, the increased activity seen on all three phases is secondary to increased blood flow.

Complications include cranial nerve palsy secondary to narrowed neural foramina, pathologic fractures as well as malignant degeneration.

References:
Siris ES. Paget's Disease of Bone. The Primer on the Metabolic Bone Diseases
and Disorders of Mineral Metabolism, 2nd Edition. Lippincott Raven, Philadelphia.
1993:375-384.

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