Which disease is characterized by excessive and haphazard bone remodeling, producing unusually weak bone and a high incidence in the spine, pelvis, femur, and skull and usually diagnosed after age 40?

• A. Paget's disease
• B. Osteoporosis
• C. Rickets
• D. Osteomalacia

Answer: (A)

Paget's disease shows a disruption of bone remodeling in which osteoclasts resorb bone excessively and chaotically, followed by a burst of osteoblast-driven bone formation that is disorganized. This creates bones that are larger and structurally weaker because the new bone has a mosaic, woven pattern rather than the normal organized lamellar structure. The condition frequently involves the spine, pelvis, femur, and skull, and is usually diagnosed after age 40 as symptoms gradually develop. Compared with osteoporosis, which is a loss of bone mass without this abnormal remodeling pattern, and with rickets or osteomalacia, which are due to defective mineralization rather than remodeling, Paget's disease is the characteristic disorder described.