Inflammation

Inflammation is a response to noxious stimuli that can be acute or chronic.

The cardinal signs of inflammation include:

• heat (calor)

• redness (rubor)

• swelling (tumor)

• pain (dolor)

• loss of tissue function (functio laesa)

Subtypes

Acute Inflammation

Acute inflammation occurs within the first few hours after an injury.

In acute inflammation, there are vascular and exudative phases.

• vascular: dilatation and increased permeability

• exudative: fluid and cells escape from permeable venules

The outcome of acute inflammation can be:

• resolution (restoration of normal function)

• non-resolution

• abscess

• organization (scarring)

• progression to chronic inflammation

Chronic Inflammation

Chronic inflammation occurs when there is a persistent damaging stimulus. This eventually heals by either scarring or granuloma formation.

Chronic inflammation differs from acute inflammation as it can last for much longer, i.e., from months to years.

Chronic inflammation is characterized by infiltration with mononuclear cells (macrophages, lymphocytes).

Outcomes of chronic inflammation include:

• a continuing response to persisting inflammatory triggers, such as infectious agents, autoimmune products, and immune complexes.

• the inflammatory cells including lymphocytes and macrophages will either be cleared or remain at the site.

• the development of giant cells along with fibrosis and/or necrosis.

Granulomatous Inflammation

Granulomatous inflammation is a specific subtype of chronic inflammation characterized by aggregation of epitheliod histiocytes. Examples of Type IV hypersensitivity reactionsn include:

• infections (tuberculosis)

• foreign bodies

• chemicals

• drugs

• idiopathic (e.g. sarcoidosis)

History and etymology

The classic signs of inflammation, namely rubor, tumor, dolor, calor et function laesa, were described by the Greek anatomist Aelius Galenus of Pergamon also known as Galen of Pergamon (129-216 AD) ^3,4.