General Pathology (PATH 303) Lecture # 9

Pathological ccification

Pathological calcification

The amount of calcium in bones, cells and fluids changes constantly.

In the blood its concentration fluctuates within a narrow range controlled by parathyroid gland.

Average = 10 mg/dl , 12 mg/dl (hypercalcemia, precipitation in tissues); 8 mg/dl (excitability); 6 mg/dl (tetany); 3 mg/dl (death)

Pathological Calcification is non-osseous (other than bones) deposition of calcium in various tissues. Have two forms:

1. Dystrophic 2. Metastatic1. Dystrophic or local calcification: Calcification of dead and dying tissues. The level of calcium in blood is usually normal.

(There is no hypercalcemia). Calcification occurs in two phases-initiation and

propagation within the cells or extra-cellularly.

Extracellular initiation occurs in small vesicles derived from degenerating cells- Ca has affinity for membrane lipids.

Initiation of intra-cellular calcification occurs in the mitochondria of dead or dying cells.

Sites of calcification: Dystrophic calcification is associated

with lesion of chronic diseases in different tissues, e.g.:

Caseous necrosis in tuberculosis. Atherosclerosis. Dead parasitic lesions like trichinosis, Onchocercosis. Thrombosis. Tumours

Gross appearance: Calcium salts appear as white granules or

grey, chalky masses. Calcium deposits have firm consistency and

gritty feelings on cutting like stones.Microscopic appearance: Calcium salts appear as blue granules or

masses with H& E. Special stain Von Kossa gives a black color to

Ca salts which maybe intracellular or extracellular.

2. Metastatic calcification: It is deposition of calcium salts in many tissues which may be normal. It is associated with disorders of calcium metabolism and there is hypercalcemia.

Causes: The common causes of metastatic calcification are:

Contd…

Hyperparathyroidism- A. Primary, due to neoplasm B. Secondary-nutritional or

renal failure (uremia) 2. Hypervitaminosis-D (Vit.D Toxicosis). Increased

absorption of Ca from intestine. Solanum and Trisetum plants have Vit. D analogue and cause toxicity.

3. Neoplasms: Lymphosarcoma and apocrine adenocarcinoma secrets parathyroid hormone- like peptides and cause hypercalcemia.

4. Calcinogenic bacteria: Tooth colonizing bacteria induce calcification and produce dental plaques.

Sites of calcification:

Metastatic calcification may occur in organ throughout the body. It is commonly observed in:

Organs which secrete or excretes acids like stomach, kidneys and lungs.

Calculi or stones in salivary glands, intestine, urinary tract, gall bladder etc.

Corpora amylacea in mammary gland alveoli, thyroid and ventricles in brain.

Gross and microscopic appearance is similar to dystrophic calcification.

Significance and results: Calcification is usually harmless. May cause hindrance to organs motility and inelasticity.