**Question:** Following are features of Paget's disease except -

A. Increased bone turnover
B. Calcification of soft tissues and blood vessels
C. Osteosarcoma
D. Joint pain and deformities

**Correct Answer:** C. Osteosarcoma

**Core Concept:**
Paget's disease (osteitis deformans) is a common osteodystrophic disorder characterized by increased bone turnover, leading to abnormal bone remodeling. It results in bone pain, deformities, and an increased risk of fractures and secondary complications. Osteosarcoma is a malignant bone tumor that is distinct from Paget's disease.

**Why the Correct Answer is Right:**
Osteosarcoma is a malignant bone tumor that occurs due to uncontrolled cell growth and differentiation, leading to bone destruction and formation of new bone. It is a separate entity from Paget's disease, which is characterized by increased bone turnover and remodeling abnormalities, but not malignant bone formation.

**Why Each Wrong Option is Incorrect:**
A. Increased bone turnover: Correct feature of Paget's disease
B. Calcification of soft tissues and blood vessels: Possible complication in advanced Paget's disease but not a primary feature
D. Joint pain and deformities: Common features of Paget's disease

**Clinical Pearl:**
Paget's disease is usually associated with a combination of symptoms and complications, such as bone pain, deformities, and fractures. While calcification of soft tissues and blood vessels can occur in advanced cases, it is not a primary feature of the disease. Osteosarcoma is a separate entity with distinct features and clinical presentations.