Definition:  Inflammation of prolonged duration (weeks and months), in which active inflammation, tissue destruction and healing occur simultaneously.

[ Acute inflammation is characterized by vascular changes, edema and neutrophilic infiltration, where as chronic inflammation is characterized by infiltration of mononuclear cells i.e. macrophages, lymphocytes and plasma cells along with tissue destruction and repair by fibrosis.]

Visit: Inflammation ; Inflammatory cells in acute and chronic inflammation ; Types of Acute Inflammation ; Chemical Mediators ; Wound Healing .

Causes:

1. Following acute inflammation due to persistence of the injurious agent or interference of healing. Example: Acute osteomyelitis

2. Repeated bouts of acute inflammation. Example: duodenal ulcer.    Peptic Ulcer

3. Low intensity injurious agents:

(i) Intracellular low toxicity microbes. Example: Mycobacterium Tuberculosis , T. pallidum , virus, fungi etc.  Infectious Disease Online-India .

(ii) Toxic agents. Example: Silica , asbestosis.   Visit: Silicosis ;

(iii) Immune reactions. Example: autoimmune diseases

Granulomatous Inflammation:

It is a distinctive pattern of chronic inflammation, in which the predominant cells are activated macrophages, which are enlarged, oval or elongated with indistinct cell boundary and called epithelioid cells. Diagnosis of granuloma rests on the identification of epithelioid cells. Epithelioid cells may coalesce  to form multinucleated giant cells (Visit: Tuberculosis ).

Two types of granuloma :

(i) Foreign body granulomas:  Incited by inert foreign bodies. Example:  suture materials, splinter, breast prosthesis, silica, asbestos etc. Foreign body granuloma ; Silicone granulomas

(ii) Immune granulomas:  It is Type IV hypersensitivity and  mediated by T-cells, typically seen in tuberculosis.

Microscopically, granuloma is characterized by aggregation of epithelioid cells surrounded by lymphocytes. Epithelioid cells  often fuse to form multinucleated giant cells. Giant cells with nuclei dispersed to the periphery of the cells are called Langhans type of giant cells.

Granulomatous Reaction Pattern of the Skin

Examples of Granulomatous inflammations:

Bacteria:  Tuberculosis (Mycobacterium Tuberculosis) ; Leprosy (Mycobacterium Leprae);  Syphilitic Gumma (T. pallidum); Cat Scratch Disease (gram-negative bacillus).

Parasite: Schistosomiasis.

Fungus: Histoplasma Capsulatum ; Blastomycosis ; Cryptococcus neoformis ; Coccidioides immitis.

Inorganic metals and dusts: Silicosis ; Berylliosis. ( Pneumoconiosis ;  Silicosis ;  Asbestosis  ; Coal Pneumoconiosis ; Talcosis )

Foreign body:  Suture materials ;  Breast prosthesis ;  Splinters. Foreign body granuloma ; Silicone granuloma

Unknown: Sarcoidosis

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Cellular Injury

Diagram showing Structural Changes in Reversible and Irreversible Cell Injury

Autolysis

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Necrosis

Coagulation (Coagulative) necrosis

Caseative necrosis

Liquefaction necrosis

Fat necrosis

Fibrinoid necrosis

Apoptosis

Gangrene

Pathologic Calcification

Hyaline Change

Atrophy

Hypertrophy

Hyperplasia

Metaplasia

Aplasia

Hypoplasia

Circulatory Anatomy, Physiology and Regulation

Normal Fluid Balance

Edema

Morphology of Edema