Tuesday, 4 February 2014

Tuberculosis

HIGH-YIELD TOPIC:-
TUBERCULOSIS
a/k/a KOCH’s disease
acid fastness – due to MYCOLIC ACID
Virulence factor --- “CORD factor”
a) PRIMARY TUBERCULOSIS
Most commonly seen in children a/w unsensitised and unexposed individuals source of organism--- exogenous most commonly starts as “LATENT DISEASE” unilateral hilar lymph enlargement
GHON’S FOCUS:-
Subpleural fibrocaseous lesion (CONSOLIDATION) of lung parenchyma (mc---lower part of upper lobe.)
microscopically contains epitheloid granulomatous inflammation
GHON’S COMPLEX:-
Consists of Subpleural ghon’s focus and involved lymph nodes.
Ghon's complex found below clavicle.
RANKE’S COMPLEX :-
ghon’s focus alongwith FIBROSIS and CALCIFICATION known as RANKE’S COMPLEX.
SIMON FOCUS
is a tuberculous (TB) nodule formed in lung apex. Due to spread of primary TB infection from elsewhere in the body to lung apex via bloodstream. Simon focus nodules are often calcified.
Fibrosis
Calcification
Pleural effusion
Erythema nodosum
Phlyctenular conjunctivitis
b) POST-PRIMARY (=SECONDARY)PULMONARY TUBERCULOSIS
Seen in previously sensitized host due to reactivation of latent primary lesions frequently a/w decreased immune status
PUHL’S LESION:-
Lesion in lung apex (upper lobe )(most commonly ---- rt lung>lt lung)
No lymph node involvement
ASSMAN FOCUS:-
infraclavicular lesion of chronic pulmonary T.B.
Lymph node involvement is RARE.
secondary TB more likely to cavitate than primary TB.
Endobronchial spread along nearby airways is relatively common finding,
resulting in relatively well-defined 2-4 mm nodules or branching lesions TREE- IN-BUD APPEARANCE on CT tuberculoma formation and miliary TB are also recognised patterns of secondary TB.
c) MILIARY PULMONARY TUBERCULOSIS
Miliary tuberculosis is uncommon but carries a poor prognosis. It represents haematogeneous dissemination of an uncontrolled tuberculous infection. seen both in primary and post-primary tuberculosis.
lungs are usually the easiest location to image.
Miliary deposits appear as 1-3 mm diameter nodules.
RICH FOCUS
is a tuberculous granuloma occurring on brain cortex that ruptures into subarachnoid space, causing
tuberculous meningitis.
WEIGERT’S FOCUS :-
Subintimal foci in pulmonary vein. ( d/t metastatic caseous TB.)
SIMOND’S FOCUS:-
Localized tb foci in liver.

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