Deposition of calcium salts in tissues other then osteoid or enamel is called pathologic or heterotropic calcification.
TYPES OF CALCIFICATION :-
Two distinct types of pathologic calcification are recognized as :-
A.] DYSTROPHIC CALCIFICATION :-
- It is characterized by deposition of calcium salt in dead or degraded / degenerated tissue with normal calcium metabolism and normal serum calcium level.
- It commonly develop in aging or damaged heart valves.
- The calcium salts microscopically appears as fine, white granules or clumps often felt as gritty deposits.
- In the pathogenesis of dystrophic calcification the final common pathway is the formation of crystalline calcium phosphate mineral in the form of an apitite similar to an the hydroxyapatite of bone.
- The process basically has two major phases : Initiation ( or nucleation ) and propagation; both can occur intracellulary and extracellulary.
B.] METASTATIC CALCIFICATION :-
- It occurs apparently in normal tissues and is associated with degraded calcium metabolism and hypercalcaemia.
- Metastatic calcification is also noticeable in dystrophic calcification.
- Since metastatic calcification occurs in normal tissues due to the hypercalcaemia, its causes would include either of the following two groups of causes :- a.) Excessive mobilization of calcium from the bone and b.) Excessive absorption of calcium from the gut.
- Metastatic calcification occurs because of the excessive binding of inorganic phosphate ions with increased calcium ion due to underlying metabolic derangement.
- Pigments are colored substances, some of which are normal constituents of cells whereas others are abnormal and collect in cells only under special circumstances.
- Pigments are of two types – they are either be exogenous (coming from outside the body) or endogenous (synthesized within the body).
- The most common exogenous pigment is carbon or coal dust, which is an unbiquitous air pollutant of urban life.
- Endogenous pigment include lipofuscin, melanin and certain derivatives of hemoglobin.
- Lipofuscin is an insoluble pigment, also known as lipochrome and wear and tear or aging pigment. Lipofuscin is composed of polymer of lipid and phospholipid complexed with protein.
- Melanin is an endogenous, non – hemoglobin – derived, brown – black pigment formed when the enzyme throsinase catalyzes the oxidation of tyrosine to dihydroxyphenylalanine in melanocytes.
- Hemosiderin is an hemoglobin – derived, golden – yellow to brown, granular pigment in which form iron is stored in the cells.
- Excesses of iron cause hemosiderin to accumulate within the cell, either as a localized process or as systemic derangement.
- The best example of localized hemosiderosis is the common bruise.
- Whenever, there are causes for systemic overload of iron, hemosiderin is deposited in many organs and tissue like increased absorption of dietary iron, impaired utilization of iron, hemolytic anemia and transfusion because the transfused red cell constituent an exogenous load of iron.
- Even though the bilirubin pigment is distributed throughout all tissues and fluids of the body, the accumulation are most evident in liver and kidney.
MULTIPLE CHOICE QUESTIONS [MCQs] :-
1.] Psammona bodies are seen in all except ?
a. Follicular carcinoma of thyroid
b. Papillary carcinoma of thyroid
c. Serous crystadenoma of ovary
2.] True about metastatic calcification is ?
a. Calcium level is normal
b. Occur in dead and dying tissue
c. Occur in damaged heart valves
d. Mitochondria involved earliest
3.] Which of the following is not a common site for metastatic calcification ?
a. Gastric mucosa
4.] Calcification of soft tissue without any disturbance of calcium metabolism is called ?
a. Inotropic calcification
b. Monotropic calcification
c. Dystropic calcification
d. Calcium induced calcification
5.] The light brown perinuclear pigment seen on H2E staining of the cardiac muscle fiber in the grossly normal appearing heart of an 83 year old man at autopsy is due to deposition of ?
c. Cholesterol metabolite
d. Anthracotic pigment
6.] Dystropic calcification is seen in ?
b. Hyper parathyroidism
c. Antheromatous plaque
d. Vitamin – A intoxication
7.] Heterotropic calcification occurs in ?
a. Ankylosing spondylitis
b. Reiter’s disease
c. Forrestier’s disease
d. Rheumatoid arthritis
e. Gouty arthritis
8.] Metastatic calcification occurs in all except ?
c. Fundus of stomach
d. pulmonary vein
9.] Dystrophic calcification is ?
a. Calcification in dead tissue
b. Calcification in living tissue
c. Calcification in decade man
10.] Psammona bodies are typically associated with all of the following neoplasms except ?
c. Papillary carcinoma of the thyroid
d. Papillary serous cystadenocarcinoma of the ovary
1.] (a) Follicular carcinoma of thyroid
2.] (d) Mitochondria involved earliest
3.] (c) Parathyroid
4.] (c) Dystropic calcification
5.] (b) Lipochrome
6.] (c) Antheromatous plaque
7.] (a) Ankylosing spondylitis
8.] (b) Atheroma
9.] (a) Calcification in dead tissue
10.] (a) Medullablastoma
1.] Textbook Of Pathology By Harsh Mohan; 7th edition; Page no. 33 – 37 , 22 – 26.
2.] Robbin’s Basic Pathology; 5th edition; Page no. 30 – 31 , 28 – 30.