Pathology of Tuberculosis

Mycobacterium tuberculosis is the organism that is the causative agent for tuberculosis (TB). There are other "atypical" mycobacteria such as M. kansasii that may produced a similar clinical and pathologic appearance of disease. M. avium-intracellulare (MAI) seen in immunocompromised hosts (particularly in persons with AIDS) is not primarily a pulmonary infection in terms of its organ distribution (mostly in organs of the mononuclear phagocyte system).

Tuberculosis is becoming a world-wide problem. War, famine, homelessness, and a lack of medical care all contribute to the increasing incidence of tuberculosis among disadvantaged persons. Since TB is easily transmissible between persons, then the increase in TB in any segment of the population represents a threat to all segments of the population. This means that it is important to institute and maintain appropriate public health measures, including screening, vaccination (where deemed of value), and treatment. A laxity of public health measures will contribute to an increase in cases. Failure of adequate treatment promotes the development of resistant strains of tuberculosis.

Patterns of Infection

There are two major patterns of disease with TB:

Primary tuberculosis: seen as an initial infection, usually in children. The initial focus of infection is a small subpleural granuloma accompanied by granulomatous hilar lymph node infection. Together, these make up the Ghon complex. In nearly all cases, these granulomas resolve and there is no further spread of the infection.

Secondary tuberculosis: seen mostly in adults as a reactivation of previous infection (or reinfection), particularly when health status declines. The granulomatous inflammation is much more florid and widespread. Typically, the upper lung lobes are most affected, and cavitation can occur.

When resistance to infection is particularly poor, a "miliary" pattern of spread can occur in which there are a myriad of small millet seed (1-3 mm) sized granulomas, either in lung or in other organs.

Dissemination of tuberculosis outside of lungs can lead to the appearance of a number of uncommon findings with characteristic patterns:

Skeletal Tuberculosis : Tuberculous osteomyelitis involves mainly the thoracic and lumbar vertebrae (known as Pott's disease) followed by knee and hip. There is extensive necrosis and bony destruction with compressed fractures (with kyphosis) and extension to soft tissues, including psoas "cold" abscess.

Genital Tract Tuberculosis : Tuberculous salpingitis and endometritis result from dissemination of tuberculosis to the fallopian tube that leads to granulomatous salpingitis, which can drain into the endometrial cavity and cause a granulomatous endometritis with irregular menstrual bleeding and infertility. In the male, tuberculosis involves prostate and epididymis most often with non-tender induration and infertility.

Urinary Tract Tuberculosis : A "sterile pyuria" with WBC's present in urine but a negative routine bacterial culture may suggest the diagnosis of renal tuberculosis. Progressive destruction of renal parenchyma occurs if not treated. Drainage to the ureters can lead to inflammation with ureteral stricture.

CNS Tuberculosis : A meningeal pattern of spread can occur, and the cerebrospinal fluid typically shows a high protein, low glucose, and lymphocytosis. The base of the brain is often involved, so that various cranial nerve signs may be present. Rarely, a solitary granuloma, or "tuberculoma", may form and manifest with seizures.

Gastrointestinal Tuberculosis : This is uncommon today because routine pasteurization of milk has eliminated Mycobacterium bovis infections. However, M. tuberculosis organisms coughed up in sputum may be swallowed into the GI tract. The classic lesions are circumferential ulcerations with stricture of the small intestine. There is a predilection for ileocecal involvement because of the abundant lymphoid tissue and slower rate of passage of lumenal contents.

Adrenal Tuberculosis : Spread of tuberculosis to adrenals is usually bilateral, so that both adrenals are markedly enlarged. Destruction of cortex leads to Addison's disease.

Scrofula : Tuberculous lymphadenitis of the cervical nodes may produce a mass of firm, matted nodes just under the mandible. There can be chronic draining fistulous tracts to overlying skin. This complication may appear in children, and Mycobacterium scrofulaceum may be cultured.

Cardiac Tuberculosis : The pericardium is the usual site for tuberculous infection of heart. The result is a granulomatous pericarditis that can be hemorrhagic. If extensive and chronic, there can be fibrosis with calcification, leading to a constrictive pericarditis.

Microscopic Findings

Microscopically, the inflammation produced with TB infection is granulomatous, with epithelioid macrophages and Langhans giant cells along with lymphocytes, plasma cells, maybe a few PMN's, fibroblasts with collagen, and characteristic caseous necrosis in the center. The inflammatory response is mediated by a type IV hypersensitivity reaction. This can be utilized as a basis for diagnosis by a TB skin test. An acid fast stain (Ziehl-Neelsen or Kinyouri s acid fast stains) will show the organisms as slender red rods. An auramine stain of the organisms as viewed under fluorescence microscopy will be easier to screen and more organisms will be apparent. The most common specimen screened is sputum, but the histologic stains can also be performed on tissues or other body fluids. Culture of sputum or tissues or other body fluids can be done to determine drug sensitivities.

Submitted By:

Similar of Pathology of Tuberculosis

Diseases Resembling Tuberculosis

Many types of mycobacteria exist; many can cause infections that produce symptoms similar to tuberculosis. The most common are a group known as Mycobacterium


Tuberculosis, commonly referred to as TB, is a chronic bacterial infection that can spread through the lymph nodes and bloodstream to any organ in your body

Post- Primary Pulmonary Tuberculosis

Post primary tuberculosis is the term used to describe lung disease, the characteristic pathological feature of which is the tuberculous cavity formed when the

A New Therapy for Tuberculosis

It is often tempting to abandon old ways for glamorous new ones. Such is certainly the case for antibiotic development. However, a recent study by Andries and

Prevention & Control of Tuberculosis

National TB Control Programme 1. National TB Control Programme: The NTP is an approach within the national health system to control TB. 2.The Aims of the NTP:

Tuberculosis in Alternative Medicine

Tuberculosis (TB) is a bacterial disease that mainly affects the lungs. In 15% of patients it affects other areas, causing swollen lymph nodes, pleurisy (

The Role of Diet in Tuberculosis

The typical Tuberculosis treatment regimen calls for 6 to 18 months of daily administration of several powerful antibiotics: usually isoniazid, rifampin,



Post new comment