Different Types of Pathological Calcification

Q. Discuss the types of calcification.

The mineralisation of body tissues with calcium is a normal physiological process in tissues like bones and teeth, termed as physiological calcification. However, sometimes the visceral tissues and other soft tissues may also get calcified in many diseased states, which is called pathological calcification. In addition to the calcium salts, smaller amounts of iron, magnesium and other minerals may also be deposited.

Pathological calcification can be broadly classified into two types: Dystrophic Calcification and Metastatic Calcification.

Dystrophic calcification: When the deposition takes place in dead or dying tissues, then it is termed as dystrophic calcification. The serum calcium levels are normal and the calcium metabolism is not deranged. Though hypercalcemia is not a prerequisite for dystrophic calcification, hypercalcemia can exacerbate it. It is seen in areas of tissue necrosis of any type. It is almost always present in the atheromas of advanced atherosclerosis, associated with intimal injury in the aorta and large arteries and characterized by the accumulation of lipids. Sometimes dystrophic calcification may also indicate organ dysfunction, e.g. calcification can develop in damaged heart valves, resulting in severely compromised valve motion. Pathogenesis involves initiation and propagation where crystalline calcium phosphate is formed as the final product.

Metastatic Calcification: Due to hypercalcemia, metastatic calcification may occur in normal tissues.

 The causes of hypercalcemia may be:
- increased secretion of parathyroid hormone (due to either primary parathyroid tumors or production of parathyroid hormone–related protein by other malignant tumors)
- destruction of bone (e.g. Paget's disease, Myeloma, Leukemia, etc.)
- Vitamin D - related disorders and sarcoidosis
- renal failure, in which phosphate retention leads to secondary hyperparathyroidism

Metastatic calcification can occur widely throughout the body but principally affects the interstitial tissues of the vasculature, kidneys, lungs, and gastric mucosa.