Main classifications of chronic inflammation

Conventionally, chronic inflammation is subdivided into 2 types.

1. Nonspecific, when the irritant substance produces a non-specific chronic inflammatory reaction with formation of granulation tissue and healing by fibrosis, e.g. chronic osteomyelitis, chronic ulcer.

2. Specific, when the injurious agent causes a characteristic histologic tissue response, e.g. tuberculosis, leprosy, syphilis.

However, for a more descriptive classification, histological features are used for classifying chronic inflammation into 3 corresponding types.

1. Chronic nonspecific interstitial inflammation. This is characterized by nonspecific inflammatory cell infiltration, e.g. chronic osteomyelitis, lung abscess. A variant of this type of chronic inflammatory response is chronic suppurative inflammation in which infiltration by polymorphs and abscess formation are additional features, e.g. actinomycosis. The inflam-

matory cell infiltration consist of lymphocytes, monocytes, plasmocytes, eosinophils and other cells.

2. Chronic nonspecific interstitial inflammation with formation of polyps and pointed condyloma. It occurs on the mucous membranes and in the areas borderline with squamous epithelium.

Polyps are the end result of prolonged chronic irritation. Nasal, cervical, colorectal polyps are common. Macroscopically they are gelatinous masses with smooth and shining surface. Microscopically they are composed of loose edematous connective tissue containing some mucous glands and varying number of inflammatory cells (lymphocytes, plasmocytes, eosinophils).

Condyloma is commonly located on the coronal sulcus on the penis or the perineal area.

3. Chronic granulomatous inflammation. This is characterized by formation of granulomas, e.g. tuberculosis, leprosy, syphilis, actinomycosis, sarcoidosis, etc. Granuloma is defined as a circum-scribed, tiny lesion, about 1 mm in diameter, composed predominantly of collection of modified macrophages called epithelioid cells, and rimmed at the periphery by lymphoid cells. The word «granuloma» is composed of granule meaning circumscribed granule-like lesion, and -oma which is a suffix commonly used for true tumours but here indicates inflammatory mass or collection of macrophages. The epithelioid cells, so called because of their epithelial cell-like appearance,

are modified macrophages which are somewhat elongated, having pale-staining abundant cytoplasm, lightly-staining nucleus and the cell membrane of adjacent epithelioid cells is closely apposed. Besides the presence of epithelioid cells and lymphoid cells, granulomas may have giant cells, necrosis and fibrosis. The giant cells are formed by fusion of adjacent epithelioid cells or by internal nucleate division without cytoplasmic division and may have 50—100 nuclei. These nuclei may be arranged at the periphery like horse-shoe or ring or clustered at the two poles (Langhans' giant cells), or they may be present centrally (foreign body giant cells). The former are commonly seen in tuberculosis while the latter are common in foreign body tissue reactions.

Necrosis may be a feature of some granulomatous conditions, e.g. central caseous necrosis of tuberculosis, so called because of cheese-like appearance and consistency of necrosis.

Fibrosis is due to proliferation of fibroblasts at the periphery of granuloma.

The following two factors favour the formation of granulomas:

1. Presence of poorly digestible irritant which may be organisms like Mycobacterium tuberculosis, particles of talc, etc.

2. Presence of cell-mediated immunity to the irritant, implying thereby the role of hypersensitivity in granulomatous inflammation.

A fully-developed tubercle is about 1 mm in diameter with central area of caseous necrosis, surrounded by epithelioid cells and one to several multinucleated giant cells (commonly Langhans's type), surrounded at the periphery by lymphocytes and bounded by fibroblasts and fibrous tissue.

Granulomatous inflammation is typical of reaction to poorly digestible agents elicited by tuberculosis, leprosy, fungal infections, schistoso-miasis, foreign particles, etc.

The outcomes of chronic inflammation depend on the type of inflammation, morphofunctional characteristic of the definite organ or tissue, where inflammation develops. Frequently sclerosis and hyalinosis may develop.

Stages of individual work in classStudy and describe macrospecimens

Fibrinopurulent pericarditis. Describe the macro-specimen, characterize the surface of the epicardium. What is the descriptive name for the specimen? Indicate the causes and outcome; possible clinical determination of pericarditis.

Purulent leptomeningitis. Characterize the stage of haemorrhage in the pia mater of the brain, state of the gyri, sulci, exudative type. What are the causes of the inflammation, its complications and outcome.

Brain abscess. Appearance of the abscess walls and the content of the space. Which type of inflammation is it? Name the causes of purulent inflammation and its outcome.

Croupous pneumonia in the stage of grey hepatization. Describe the appearance of the lungs; aeration, pleura state, the character of the exudate. Etiological factors, the outcomes of the inflammation and possible complications.

Diphtheroid colitis. Describe the macro specimen. Characterize the thickness of the intestinal walls, the types of the film covering the mucous layer. Name the disease and state under which the above inflammation develops.

Unicameral hepatic echinococcosis. Describe the cavity shape, its internal layer, cyst contents. The appearance of external layer of the cyst side. Name the sequence of changing the tissue reaction to the zone of parasitical inculcation.

Condyloma. Characterize the appearance of condyloma, its sizes. Describe the character of the growth. Name the localization of condyloma. Kind of the productive inflammation.

Polyp of small intestine. Describe the appearance of the intestine from the side of the tunica. Name the type of productive inflammation and possible complications, outcomes.

Miliary pulmonary tuberculosis. Characterize the appearance of the nodule and the nature of the process. Describe the colour, size, quantity of them. Give the definition with the regard of the character of pathological process and its morphological form, etiology and degree of the prevalence. Name the way of pathogen dissemination. Translate the term «miliary». In what forms of tuberculosis is it observed? Possible outcomes of granuloma; the causes of death.

Syphilitic mesaortitis. Pay attention to localization of the pathological process with the regard of the aorta part. Describe the appearance of the aorta in the place of localization of pathological process. Pathogenesis of the disease. Name the figurative name of the changing aorta intima in the place of direct injury and the kind of pathological process (which

underlie in the aorta changing), its form with the regard of etiology and morphology. In which period of syphilis do you observe these changes? Name the possible complication.

Hepatic solitary gummas. Pay attention to the heterogeneous hepatic appearance. Define the form of the gumma, its colour, periphery of the gumma. Give the definition of the term «gumma» with the regard of the character of the pathological process, its morphological form, etiology and degree of the prevalence. Translate the term «solitary». In which period does syphilis develop in the gummas? Name the outcomes. Explain the essence of the changes in the liver.