Morphologic Patterns of Inflammation

]]Acute Inflammation]]

• dilation of small blood vessels
• accumulation of leukocytes and fluid in the extravascular tissue

Classification according to the morphologic appearance:

• Non-suppurative Inflammation
    * Catarrhal inflammation
    * Serous inflammation
    * Fibrinous inflammation
    * Hemorrhagic inflammation
    * Membranous/pseudo-membranous inflammation
    * Necrotizing (gangrenous) inflammation
    * Allergic inflammation
• Suppurative Inflammation
    * Localized:
      * Abscess inflammation
      * Furuncle
      * Carbuncle
    * Diffuse:
      * Cellulitis

]]Acute Non-suppurative Inflammation]]

• without pus formation

Catarrhal inflammation

• $excess mucus secretion due to inflammation of mucus membranes$

^^Site^^: mucous membranes

%%Example%%: common cold (rhinovirus), influenza

@@Gross appearance:@@ congestion, edema, mucus secretion

==Microscopic examination: ==

• blood vessel dilation, congested (filled with blood)
• excess mucus on epithelial surface
• few or absence of neutrophils

Serous Inflammation

• $watery protein-poor fluid$ (effusion)
• typically does not contain microbes or large numbers of leukocytes
• Derived from:
    * serum
    * mesothelial cell secretion

^^Site^^: spaces created by cell injury or into body cavities lined by the peritoneum, pleura, or pericardium.

%%Examples%%: skin blister (burn), pleural effusion (pleurisy)

@@Gross appearance@@: congested surface, watery effusion

Fibrinous Inflammation

• $fibrinous exudate$

^^Site^^: lining of body cavities, (meninges, pericardium, and pleura)

%%Example%%: serosal surfaces (fibrinous pericarditis)

Hemorrhagic Inflammation

• $exudate rich in red blood cells$

%%Example%%: severe capillary damage (anthrax, plague)

Membranous/Pseudo-membranous Inflammation

• $necrotic membrane on mucus surfaces$

%%Example%%: diphtheritic pharyngitis, bacillary dysentery

@@Gross appearance@@: greyish membrane on mucosal surface

==Microscopic examination: ==

• necrotic mucosa
• fibrin and inflammatory cells adherent to mucosal surface

Necrotizing (Gangrenous) Inflammation

%%Example%%: gangrenous acute appendicitis, gangrene of the foot

Allergic Inflammation

%%Example%%: bronchial asthma

==Microscopic examination: ==

• exudate rich in eosinophils
• extensive edema

]]Acute Suppurative (Purulent) Inflammation]]

• purulent exudate (pus): fluid, necrotic cells, and pus cells (dead neutrophils)

Localized

• abscess formation

==Organisms==: pyogenic bacteria (Staphylococcus aureus)

Diffuse

$<strong>Cellulitis</strong>$: diffuse suppurative inflammation

^^Site^^: subcutaneous tissue (orbit, pelvis, scrotum, mediastinum)

==Organisms==: Streptococcus hemolyticus

<<Chronic Inflammation<<

• Chronic “non-specific” or diffuse inflammation
• Chronic specific inflammation

<<Diffuse Non-specific Inflammation<<

• diffuse chronic inflammatory cell infiltrate

%%Example%%: chronic pyelonephritis, chronic cholecystitis

<<Chronic Specific Inflammation (Granuloma)<<

• caseating granulomatous inflammation
    * %%Example%%: Tuberculosis
• non-caseating granulomatous inflammation
    * %%Example%%: leprosy, syphilis, schistosomiasis, sarcoidosis and foreign body granuloma