Pathological calcification

It is the abnormal deposition of calcium salts in tissues. It can be dystrophic or metastatic.

Dystrophic calcification

It is the deposition of calcium in dead or non-viable tissues in the presence of a normal serum calcium level. Sites are necrotic areas, fat necrosis, atheromas and damaged heart valves. Periventricular calcification is seen in congenital CMV infection. It is macroscopically felt as gritty, white, granular deposits. On microscopy, they appear as basophilic deposits on H and E stain. It may form lamellated structures in some conditions called “psammoma bodies”. Calcium phosphate is the compound which gets deposited. Calcification is initiated either by mitochondria of dead or dying cells or by membrane phospholipids. Phosphatases cleave membrane phospholipids to release phosphate which then binds with calcium and forms locally propagating calcium phosphate crystals that further damages the cell membrane.

Metastatic calcification

It is the deposition of calcium in normal tissues in the presence of a deranged calcium metabolism and hypercalcemia and/or hyperphosphatemia. Any condition causing hypercalcemia or hyperphosphatemia, such as hyperparathyroidism, renal failure, vitamin D toxicity, sarcoidosis etc. can lead to metastatic calcium deposits in the gastric mucosa, kidneys, lungs, arteries etc. Microscopic and gross appearance resembles dystrophic calcification. Basal ganglia calcification is seen in hypoparathyroidism.