**Question:** Paget's disease of bone is a chronic disease of the

A. Cervical spine
B. Pelvic bones
C. Long bones
D. Vertebrae

**Correct Answer:** C. Long bones

**Core Concept:** Paget's disease of bone (PDB) is a chronic disorder characterized by abnormal bone remodeling. In PDB, osteoclasts, which are responsible for breaking down and reshaping bone, become overactive and cause bone remodeling to be more intense and prolonged than normal. This leads to bone deformities, increased bone mass, and an increased risk of fractures.

**Why the Correct Answer is Right:** PDB primarily affects long bones, including the femur, tibia, and fibula. These bones are more susceptible to the disease due to their large size, which allows for more extensive remodeling and the potential for significant structural abnormalities. The disease is less common in smaller bones like the cervical spine, pelvic bones, and vertebrae.

**Why Each Wrong Option is Incorrect:**

A. The cervical spine: While some cases of PDB may involve the cervical spine, it is not the primary site affected by the disease. Long bones are more common targets for the disease.

B. Pelvic bones: PDB primarily affects long bones, making pelvic bones an incorrect answer choice as they are less commonly involved.

D. Vertebrae: Similar to the cervical spine, PDB may affect vertebrae in some cases, but the disease is less common in this area compared to long bones.

**Clinical Pearl:** Paget's disease is named after Sir Thomas Paget, who first described the condition in 1877. Understanding the disease's primary target, long bones, is essential for recognizing the clinical manifestations and making an accurate diagnosis.