chronic inflammation

• Chronic inflammation is defined as inflammation of prolonged duration (weeks or months) where

• Continuing inflammation,

• Tissue destruction and

• Healing proceeds simultaneously.

Infiltration by mononuclear cells◦ Macrophages◦ Lymphocytes◦ Plasma cells

Tissue destruction

Repair◦ Angiogenesis (formation of new blood vessels)◦ Fibrosis

1] Bacterial - TB, Syphilis, Leprosy

2] Fungal – Cryptococcal

3] Parasitic – Schistosomias

4] Miscellaneous - Sarcoidosis, Crohn’s disease

Distinctive pattern of chronic inflammation characterized by formation of granulomas.

Characterized by presence of◦ Activated macrophages ◦ Lymphocytes◦ Occasional plasma cells

Tuberculosis is caused by Mycobacterium tuberculosis

Primary tuberculosis ◦ Usually seen in children◦ Due to initial (first) infection

Secondary tuberculosis◦ Seen in adults◦ Reactivation of primary infection

Focus of tuberculous inflammation◦White to tan colored lesion

◦Round, irregular borders

◦Central necrosis (caseation)

◦Soft, granular, cheesy material

Extensive necrosis drains out the necrotic core

Leads to cavity formation

Extensive spread leads to formation of multiple millet sized granulomas in the same organ

Involvement of lymph nodes gives them a matted appearance

The centres are filled cheesy necrotic material

Characterised by presence of ulcers which are transverse (perpendicular to the long axis of the intestines)

Compared with ulcers caused by typhoid which are longitudinal

Caseous necrosis◦ Pink structureless centre◦ Surrounded by

lymphocytes

Epitheliod cells◦ Activated macrophages◦ Pink granular cytoplasm◦ Slipper shaped nucleus

Giant cells◦ Large mass of cytoplasm◦ Numerous nuclei

H&E stained section showing a granuloma with central caseation necrosis surrounded by a collar of lymphocytes, epithelioid cells and giant cells

Syphilis is a sexually transmitted disease caused by Treponema Pallidum and has 3 stages

Primary stage- chancre in the genital region

Secondary stage- lymphadenopathy and skin lesions

Tertiary stage- aortitis

Form of cardiovascular syphilis occurring in 80% of tertiary syphilis

Affects proximal aorta

Tree bark like appearance

H & E stained sections showing fibrosis of the media of the vessel wall and infiltration by lymphocytes and plasma cells.

Granular and pink appearance of tissue in a healing ulcer

Granulation tissue is composed of◦ Fibroblasts,◦ Newly formed small

blood vessels and ◦ Inflammatory cells

Mycetoma is a chronic subcutaneous infection

Initially presents as a nodule

Later swelling and multiple discharging sinuses

Grossly visible granules of various colors seen extruding from sinuses

Gross - solitary, small (1-2.5cm), punched out with sharply defined margins, deeply penetrating.

gastric ulcer shows indrawing of the mucosal folds toward the ulcer margins due to contraction of fibrous tissue. Healed chronic gastric ulcer shows radiating folds pointing to the site of the healed ulcer

BENIGN ULCER Flat margins in level with

surrounding mucosa Mucosal folds converge

towards the ulcer (radiating/spoke wheel pattern)

MALIGNANT ULCER Are larger, bowl shaped

with elevated and indurated mucosa at the margin

Gastric ulcer :Microscopically, the ulcer here is sharply demarcated, with normal gastric mucosa on the left falling away into a deep ulcer whose base contains infamed, necrotic debris..

Granular and pink appearance of tissue in a healing ulcer

Gross examination- floor of the lesion contains pink granulations composed of the vascular connective tissue, while the edges are sloping and bluish white.

At high magnification, granulation tissue has capillaries, fibroblasts, and a variable amount of inflammatory cells (mostly mononuclear, but with the possibility of some PMN's still being present).

MICROSCOPIC EXAMINATION

• Granulation tissue is composed of proliferating fibroblasts, newly formed small blood vessels and varying number of inflammatory cells which are initially polymorphs but in later stages macrophages and lymphocytes predominate.

The wall of an abscess that is organizing has granulation tissue, seen here at the left. The purulent exudate with some hemorrhage is seen at the right in the

abscess center.