## **Core Concept**
Scurvy is a disease caused by a lack of vitamin C (ascorbic acid) in the diet. Vitamin C is essential for the production of collagen, a protein that gives structure to skin, bones, muscles, and tendons. The primary metabolic bone disorder in scurvy relates to the defective production of collagen.

## **Why the Correct Answer is Right**
The correct answer, **D. defective collagen synthesis**, is right because vitamin C is crucial for the hydroxylation of proline and lysine residues in collagen. Without vitamin C, collagen synthesis is impaired, leading to weakened connective tissue, including bone. This results in the characteristic features of scurvy, such as poor wound healing, joint pain, and bone abnormalities.

## **Why Each Wrong Option is Incorrect**
- **Option A: increased bone resorption** - While bone resorption may occur in scurvy due to the overall weakening of bone structure, it is not the primary metabolic bone disorder.
- **Option B: decreased bone formation** - This option is closer to the truth but is not as specific as defective collagen synthesis. Decreased bone formation is a consequence of defective collagen synthesis.
- **Option C: impaired mineralization** - Impaired mineralization is more characteristic of conditions like rickets or osteomalacia, which are related to deficiencies in vitamin D, calcium, or phosphate.

## **Clinical Pearl / High-Yield Fact**
A key clinical pearl is that scurvy can present with a range of symptoms from fatigue and malaise to specific signs like gingivitis, joint pain, and poor wound healing. A classic sign is the development of perifollicular petechiae. Importantly, scurvy can be diagnosed and treated with vitamin C supplementation, making it a critical condition to recognize, especially in populations at risk of malnutrition.

## **Correct Answer:** . **defective collagen synthesis**