Immunopathology - Week 2 - Types of Necrosis

Question 1

List the 6 types of Necrosis

Answer 1

1. Coagulative Necrosis
2. Colliquative (Liquefactive)
3. Gangrenous Necrosis
4. Caseous Necrosis
5. Fat Necrosis
6. Fibrinoid (Hyaline) Necrosis

Question 2

Describe Coagulative Necrosis.

Answer 2

Characterised by preservation of the
basic structural outline of necrotic cells or
tissue

• It is the most common type of necrosis in
  the body, occurring in solid organs e.g.
  heart, kidney, spleen, and liver
• Myocardial infarction is a prime example

Question 3

Describe Colliquative (Liquefactive).

Answer 3

• This is characteristic of focal bacterial
  infections
  Ø Stimulate leukocytes
  Ø leukocytes release hydrolytic enzymes
• This may be seen in an abscess, where
  the tissue has been destroyed and replaced
  by a thick white-yellow fluid called pus.
• Hypoxic death of cells within the central
  nervous system also results in liquefactive
  necrosis.

Question 4

Describe Gangrenous Necrosis.

Answer 4

• This does not refer to a specific pattern of
  necrosis.
• The term refers to ischaemic coagulative
  necrosisof a limb (or part of it)
• When there is superimposed infection with a
  liquefactive component, the lesion is called
  wet gangrene.
• Gangrene of the toes and feet is commonly
  encountered in advanced and long-standing
  diabetes mellitus, and it is due to advanced
  peripheral artery disease (atherosclerosis)
  leading to severely impaired blood flow.

Question 5

Describe Caseous Necrosis.

Answer 5

Caseous necrosis is a distinctive form
of necrosis encountered most often in
foci of tuberculosis infection.

• The term ‘caseous’ is derived from the
  cheesy (cottage-cheese like) white
  gross appearance of the central
  necrotic area.

Question 6

Describe Fat Necrosis.

Answer 6

Fat necrosis describes focal areas of fat
destruction.

The Enzymatic type
* typically occurs in acute pancreatitis
* Activated pancreatic proteolytic and lipolytic
enzymes escape from pancreatic cells and
ducts
Ødestroying and liquefying fat cells in the
pancreatic tissue and peritoneal cavity and
hydrolysing the triglycerides contained within
them
* The released fatty acids combine with
calcium to produce grossly visible chalky
white areas of insoluble calcium soaps

The Traumatic type
* occurs when adipose tissue in any site is
injured by trauma e.g. a blow to the breast

Question 7

Describe Fibrinoid (Hyaline) Necrosis.

Answer 7

• Occurs in connective tissue within blood
  vessel walls
• Most commonly associated with
  hypertension and autoimmune diseases
• The collagen becomes denatured,
  fibrinogen from blood enters necrotic
  tissue and is converted to fibrin.