Tuberculosis pathogenesis

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Types , Pathogenesis & Clinical Picture of Tuberculosis

TYPES

Primary infection

Reactivation TB

PRIMARY INFECTION (usually in children)

It is response to first exposure to M. tuberculosis.

Usually pulmonary infection - at periphery of mid zone of lung (sub-pleura)

TB bacilli are engulfed by macrophages - those survive multiply in macrophages ? carried to hilar lymph nodes

Dissemination to other organs through blood stream can occur

Cell mediated immunity & Hypersensitivity

Develop 2-6 weeks after infection.

Macrophages containing TB bacilli present to competent

T-lymphocytes? lymphokines ? attract monocytes and transform them to activated macrophages ? surround the infected area ? slow down bacterial multiplicaiton.

° Leads to granuloma formation

Tubercle (microscopic granuloma) formation at subpleural area

Consists of :

Many epithelioid cells (activated macrophages)

Multinucleated giant cells (formed by fusion of macrophages)

Surrounded by lymphocytes

° Known as Ghon focus.

REACTIVATION TUBERCULOSIS

1. Occur due to reactivation of an old focus in elderly due to:

Malnutrition

Diabetes mellitus

Alcoholism