U01.04.008 Types of calcification

Calcification refers to the deposition of calcium salts in tissues. Under microscopic examination, calcium deposits appear deeply basophilic on H&E staining. There are two primary types of calcification: dystrophic calcification and metastatic calcification.

1. Dystrophic Calcification

Ca2+ Deposition: Occurs in abnormal (diseased) tissues.
Extent: Tends to be localized, such as in calcific aortic stenosis.
Associated Conditions:
- Tuberculosis (lung and pericardium) and other granulomatous infections
- Liquefactive necrosis of chronic abscesses
- Fat necrosis
- Infarcts
- Thrombi
- Schistosomiasis
- Congenital CMV, toxoplasmosis, rubella
- Psammoma bodies
- CREST syndrome
- Atherosclerotic plaques can become calcified
Etiology: Secondary to injury or necrosis.
Serum Ca2+ Levels: Typically normal.

2. Metastatic Calcification

Ca2+ Deposition: Occurs in normal tissues.
Extent: Widespread, diffuse calcification.
Associated Conditions:
- Predominantly affects interstitial tissues of the kidney, lung, and gastric mucosa, where these tissues lose acid quickly, creating a low pH environment that favors Ca2+ deposition.
- Nephrocalcinosis of collecting ducts may lead to nephrogenic diabetes insipidus and renal failure.
Etiology: Secondary to hypercalcemia or high calcium-phosphate product levels.
- Common causes include primary hyperparathyroidism, sarcoidosis, hypervitaminosis D, chronic kidney disease with secondary hyperparathyroidism, long-term dialysis, calciphylaxis, and multiple myeloma.
Serum Ca2+ Levels: Usually abnormal.

Table: Comparison of Dystrophic and Metastatic Calcification

Feature	Dystrophic Calcification	Metastatic Calcification
Ca2+ Deposition	In abnormal (diseased) tissues	In normal tissues
Extent	Localized (e.g., calcific aortic stenosis)	Widespread (diffuse, metastatic)
Associated Conditions	TB, granulomatous infections, necrosis, infarcts, etc.	Interstitial tissues of kidney, lung, gastric mucosa, etc.
Etiology	Secondary to injury or necrosis	Secondary to hypercalcemia or high calcium-phosphate levels
Serum Ca2+ Levels	Normal	Usually abnormal

Table: Comparison of Dystrophic and Metastatic Calcification

Points to Remember

Dystrophic calcification occurs in diseased tissues with normal serum calcium levels.
Metastatic calcification occurs in normal tissues due to elevated serum calcium levels or high calcium-phosphate product.
Histological Appearance: Calcium deposits are basophilic on H&E stain.
Clinical Implications: Dystrophic calcification is associated with localized tissue damage, while metastatic calcification can lead to widespread organ dysfunction, particularly in the kidneys and lungs.

USMLE Step 1 Review Series

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U01.04.008 Types of calcification

1. Dystrophic Calcification

2. Metastatic Calcification

Table: Comparison of Dystrophic and Metastatic Calcification

Points to Remember

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