**Core Concept**
Pathologic calcification refers to the accumulation of calcium salts in tissues, which can occur due to various metabolic disorders, injury, or disease processes. Normal calcium metabolism is characterized by a balance between calcium absorption, excretion, and homeostasis, regulated by hormones such as parathyroid hormone (PTH), vitamin D, and calcitonin.

**Why the Correct Answer is Right**
The correct answer is associated with metastatic calcification, where calcium salts precipitate out of solution in the setting of hypercalcemia. This can occur due to an imbalance in calcium metabolism, often seen in conditions such as hyperparathyroidism, vitamin D toxicity, or malignancy. In these cases, the body's normal mechanisms for regulating calcium levels are overwhelmed, leading to an excess of calcium ions in the blood.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because dystrophic calcification is a type of pathologic calcification that occurs in the setting of tissue injury or necrosis, where normal calcium metabolism is disrupted. It is often seen in conditions such as atherosclerosis, osteoarthritis, or after trauma.

**Option B:** This option is incorrect because idiopathic calcification is a rare condition where calcium deposits form in the absence of any underlying metabolic disorder. However, it is not a characteristic of normal calcium metabolism.

**Option C:** This option is incorrect because calciphylaxis is a condition characterized by calcification of small blood vessels, often seen in patients with end-stage renal disease. It is a result of abnormal calcium metabolism, not normal calcium metabolism.

**Clinical Pearl / High-Yield Fact**
Remember that pathologic calcification can occur due to a variety of underlying conditions, and it is essential to investigate the underlying cause to manage the condition effectively.

**Correct Answer:** D