• Deposition of calcium salts in tissues other than osteoid or enamel is called pathologic or heterotopic calcification.• Classified into:
DYSTROPHIC CALCIFICATION• Macroscopic deposition of Ca salts in dead or degenerated tissue(injured tissues).• It represents extracellular deposition of calcium from circulation or interstitial fluid.• Its often visible to naked eye and ranges from gritty sand like grains to firm rock hard material• It requires persistence of necrotic tissue.
• Caseous necrosis in tuberculosis is the most commen site and has no functional consequences.• Dystrophic calcification may also occur in crucial locations such as in mitral or aortic valves after rheumatic fever. In such instances calcification leads to impeded blood flow because it produces inflexible valve leaflets and narrowed valve orifices(mitral and aortic stenosis).
• Dystrophic calcification in artherosclerosis leads to narrowing of vessels. It also plays a role in diagnostic radiography.• Mammography is based on detection of calcification in breast cancer.• Diagnosis of congenital toxoplasmosis, an infection involving the CNS is suggested by visualization of calcification in infant brain.
METASTATIC CALCIFICATION• It reflects deranged calcium metabolism, a change associated with an increased serum calcium concentration.• Any disorder that increases the serum calcium level can lead to calcification in inappropriate locations• Its seen in various disorders like chronic renal failure, vitamin D intoxication etc.
CAUSES OF METASTATIC CALCIFICATION1.Increased secretion of parathyroid hormone2.Destruction of bone tissue as in tumors of bone marrow3.Vit D related causes –vit D intoxication.4.Renal failure
OTHER FORMS OF CALCIFICATION• Formation of stones containing calcium carbonate in sites such as gall bladder, renal pelvis and pancreatic duct.• Under certain conditions the mineral salts precipitate from solution and crystallize around foci of organic material.
CALCINOSIS• Presence of calcification on or under the skin.• There are two forms -calcinosis circumscripta -calcinosis universalies Calcinosis circumscripta as the name suggests it’s a circumscribed form and calcinosis universalies is often associated with scleroderma and sometimes dermatomytosis.
HISTOLOGY• In routine H&E stains stained sections, Ca salts appear as deeply basophilic, irregular and granular clumps.• Calcium deposits can be confirmed by special stains like silver impregnation method producing black color, and alizarin red S that produces red staining.